The Scuba Expert Let's Get Wet

Responses to Heat and Cold Underwater

diverjamesradio@gmail.com (Diver james) — Sun, 03 Mar 2013 18:05:00 +0000

HEAT

Divers need to be more concerned about heat before and after a dive than during a dive. Even in warm water the body gets cool, so than the primary concern is with heat as a result of the above water activities.

When the body temperature rises, weather from a rise due to the exposure suit, or to the fact that the sun is out, or a combination of those, the body goes through several cooling mechanisms to protect the core temperature.

Initially, skin capillaries dilate, allowing heat from the blood to radiate to the skin. Perspiration follows, which cool the skin. If the core temperature remains high, the pulse races, to help circulate more blood to help cool the body. These responses continue until the core temperature returns to normal.

COLD

A diver's physiology also reacts the same to a temp drop to protect the core temperature. Water conducts heat more than 20 times faster than in air and requires much more heat to raise its temperature. This means temperature that seems just right in the air, may be considered cold underwater.

With out the proper exposure protection, the average diver will be dangerously cold in half an hour in 40 deg water. For the majority of divers, water must be warmer than 80 deg to dive with out a suit.

By insulating the diver, the suit will extend dive times by slowing the cooling process, and making the body efforts more effective.

Divers with more fat tissue tends to loose heat more slowly than those that are thinner.

As the body cools, temperature centers in the hands, feet and head trigger heat conserving response that begin a change in circulation. Blood flow to the extremities slows through vasoconstriction to reduce heat loss from the blood through the skin. If vasoconstriction does not sufficiently maintain the core temp then the body reacts by triggering shivering. Shivering signals a losing battle with the cold. Once this starts, you need to get out of the water and begin the warming process.

A diver extends the bodys ability to maintain the core temperature through proper use of exposure suits and diving techniques. The head loses heat because the body can not reduce blood flow to the brain. Therefore a wet suit hood makes a huge difference in reducing heat loss.

Now lets talk about wet suit compression. As you dive, the suit which has large air cells begin to shrink. Meaning that the deeper you go the less protection you have to the cold. And if the suit is old than the protection is lost to a greater extent.

Divers Alert Network (DAN)

diverjamesradio@gmail.com (Diver james) — Sun, 03 Mar 2013 18:05:00 +0000

If you are an active diver, you need what I am going to bring up next. Divers Alert Network (DAN) is an organization that offers dive insurance, and a multitude of training classes. It is not associated with any one dive organization, but to diving in general. At the present time there are at least 14 different classes offered. I am going to touch on a few of them here. If you ever have a chance to get to Durham, NC, stop in, they will give you a tour. In fact, they can also arrange for you to see the Chambers at Duke University Hospital.

Oxygen First Aid for Scuba Diving Injuries
As a recreational diver, you can receive training to provide vital first aid that can make a difference to a scuba diver with decompression illness. The DAN Oxygen Provider Course provides entry-level training in the recognition and management of possible diving-related injuries using emergency oxygen first aid.

Advanced Oxygen First Aid for Scuba Diving Injuries
This advanced-level program is designed to train existing DAN Oxygen Providers to use the MTV-100 or a Bag Valve Mask while providing care for a non-breathing injured diver.

First Aid for Hazardous Marine Life Injuries
Serious hazardous marine life injuries are rare, but most divers experience minor discomfort from unintentional encounters with fire coral, jellyfish and other marine creatures. This course teaches divers to minimize these injuries and reduce diver discomfort and pain.

On-site Neurological Assessment for Divers
Learn how to conduct a neurological assessment on a potentially injured diver in this course. The information gained in this assessment can help convince a diver of the need for oxygen first aid, and help a dive physician determine the proper treatment.

Diving Emergency Management Provider Program
Learn the knowledge and skills from several courses into one single approach to dive emergency management.

Diving Emergency Specialist (DES)
Learn about DAN’s new recognition program for divers who are interested in dive safety.

Diving Medical Technician
Take the next step in diving education. Become a DMT and learn about providing care for divers involved in dive accidents.

Click on this picture above to be taken directly to the Duke University Hyperbaric Chambers and Medicine Department. There is also a link to see the complete layout of the 7 chambers. Check out the photo album on the site for more pictures - (past and present).

Layout of Hyperbaric Chambers Check this out, you will be amazed.

Click on these two pictures to see an enlarged view of the control panels. Click on the above small pictures to go to DAN Specialty Courses.
There is more to DAN then I can cover here in this short time. You need to go to the web site and check it out. Divers Alert Network

Better Watch Out If You Hold Your Breath Underwater

diverjamesradio@gmail.com (Diver james) — Sun, 03 Mar 2013 18:05:00 +0000

There are 4 types of injuries that can occur to the lungs by holding your breath on ascent.
LUNG EXPANSION INJURIES IN GENERAL
Most body air spaces respond to pressure decrease with neither complications nor voluntary action by the diver. The Lungs respond to this as well, provided the diver breathes continuously to them keep equalized to the declining pressures. If the diver holds their breath or air traps within a section of the lungs, and as pressure declines expanding air will almost always cause an over-expansion injury.

The "GOLDEN RULE" in diving - never hold your breath while on scuba and while underwater. Panic and ignorance have been the causes of divers holding their breath. Nausea, choking and carelessness have also been causes to this as well.

Obstruction in the lungs may also trap air in certain parts and in effect "hold its breath." A chest cold, or respiratory infection can cause mucus accumulation and cause an obstruction. Smoking has also been implicated in these injuries.

Lung injuries can occur from even a small amount of over-pressurization. Research has shown that starting with full lungs, holding ones breath and surfacing can have an injury in as little as a 3 to 4 feet distance.

Rather than the lungs bursting like a balloon, an over-pressurization tears the lungs. The injury does not occur from the tear to the lungs, but from the air escaping and entering the tissues and / or the bloodstream. Lung injuries can result in 1 of 4 ways: Air embolism, Pneumothorax, mediastinal emphysema, and subcutaneous emphysema.

Any lung injury causes pulmonary capillaries and alveoli to rupture, mixing blood and air in the lungs. This results, often times, to the victim coughing up blood.

AIR GAS EMBOLISM (AGE)
This is the most serious type of lung over-pressurization injury. This results was the air enters the blood stream from a rupture of the alveoli into the pulmonary capillaries, causing an air embolism or arterial gas embolism. Click on image for larger view.

An embolism is any foreign object that enters the bloodstream that blocks its flow. An air embolism is the same but now it is an air bubble that blocks the flow of blood. So as you ascend the once small bubbles become larger and larger due to the expanding nature of the ascent. This is a bubble on the arterial side of the circulation.

Air enters the bloodstream in the lungs flows through the pulmonary vein into the heart, to the left side of the heart into the aorta and then the arterial system. This air bubble can lodge almost anywhere in the circulatory system - can cause severe damage by blocking blood flow to the tissue.
The first main branch off the aorta which include the carotids. The carotids supply the majority of blood to the brain. If bubbles travel into the carotids, which is likely, they will go to the brain and cause cerebral air embolism.

The bubbles deny the brain of oxygenated blood, which causes a stroke. The symptoms include dizziness, confusion, shock, personality changes, unconsiouness, and death. Compared to DCS, the effects of cerebral air embolism and other lung injuries tends to be rapid and dramatic. DCS tends to be delayed.

If the bubbles were to miss the carotids and block the coronary arteries, the result would be a heart attack.

PNEUMOTHORAX
If the overpresurized lung tears at it surface, the expanding air leaks between the lungs and the pleural lining (chest wall), causing the lung to collapse, either partially or entirely. This collapsed lung is called a pneumothorax.

This is not nearly as life threatening as an AGE because the victim, in most cases, still has a working lung to breathe from. This collapse lung causes severe chest pain, and may cause the victim to cough up blood.

There is another form of this condition called spontaneous pneumothorax. This occurs with out the expansion of the lungs but through a weakness in the lung itself. This causes a sudden tearing and collapse of the lung.

This condition is uncommon, but can be more serious than the standard pneumothorax. especially if it happens underwater. This type can be aggravated on ascent, when the air pressing on the collapsed lung expands, increasing the pressure of the injured lung.

Since spontanous pneumothorax tends to recur, it inhibits further diving till surgery is performed to correct the problem. Since out a physician who specializes in pulmonary dive medicine. CLICK ON THE PICTURE FOR A BETTER VIEW

MEDIASTINAL EMPHYSEMA

Mediastinal means center of the chest.. This is sometimes called pneumomediastinum, is far less serious that air gas embolism and pneumothorax

This condition, air accumulating in the mediastinum presses on the heart and major blood vessels interfering with circulation. A victim may feel faint and short of breath due to impaired circulation. CLICK ON THE PICTURE TO SEE THE AIR BUBBLES IN THE MIDDLE OF THE CHEST.

SUBCUTANEOUS EMPHYSEMA

This occurs frequently with mediastinal emphysema as air seek its way from the mediastinum, and folowing the path of least resistence, into the soft tissues at the base of the neck.

Air accumulates under the skin in this area. This causes the victim to feel a fullness in the neck and to experience a voice change. The skin may crakle if touched. CLICK ON THE PICTURE TO SEE THE AIR RISE TO THE NECK REGION.

FIRST AID

The first aid for both the decompression sickness and lung overexpansion injuries are the same. You can say that the first aid for the Decompression illess injuries are the same. In fact you do not have to determine on site which you are dealing with to start giving aid to the diver.

Give 100% oxygen to the diver

Simply put, breathing 100% O2 accelerates diffusion of nitrogen from the body to slow and reverse bubble growth, and help bubble elimination. Breathing oxygen also raises the blood oxygen levels and maximizes the effectiveness of the blood that does reach the affected areas. Make sure the air ways are clear and treat for CPR if needed. The best first aid is to get them to a medical facility for proper care.

Now to the lung injuries FIRST AID

Three out of the four conditions are not immediately life threatening, the presence of any of these conditions indicates a lung over-expansion injury has occured. The AGE is the most life threatening and therefore when first aid is given, they treat any of these conditions as though they have AGE.

AGE needs immediate compression to diminish the bubbles in the bloodstream and force them into solution. This restores blood flow to the tissues. None of the other conditions require decompression, provided there is no AGE.

Pneumothorax requires surgical removal of the air from between the collapsed lung and the pleural lining, followed by a lung reinflation.

Mediastinum and subcutaneous emphysema will dissipate on their own as the blood slowly reabsorbs the trapped air. Breathing oxygen can speed up the reaborbtion process.

REMEMBER DO NOT HOLD YOUR BREATH WHILE DIVING ON SCUBA.

Regulators and the Environmental Seal

diverjamesradio@gmail.com (Diver james) — Sun, 03 Mar 2013 18:04:00 +0000

Regulators or regulator systems are really composed of many parts. The stage that attaches to the tank is known as the first stage, then comes the long air hose. This in turn is followed by the 2Nd stage, the part that actually goes into your mouth so you can breath the air.

First stage role is to accept the 3000 psi cylinder pressure coming from the tank and reduces it to an ambient pressure plus a preset intermediate pressure. It is here at second stage that its role is to reduce this ambient-plus-intermediate pressure to simply an ambient pressure so you can breathe off it. At this point we will not go into great detail on the exact mechanisms involve with this reduction.

Some first stages offer environmental sealing. This is where the first stage is completely sealed off from the water and air. Where as non-environmentally sealed regulators are open to the water temps and debris.

There are many ways to group regulators: piston vs diaphragm first stages, balanced vs unbalanced, downstream vs pivot valves, open vs closed. Even on these listed there are many combinations. Just understand there are many variations.

Still another way is what I will call non-sealed and sealed regulators. You can see on the non-sealed there are small holes on the sides, where as on the sealed the holes are missing. This is the easliest way to tell the difference.

In the sealed regulators, the water pressure doesn't act directly on the piston or diaphragm. Instead it acts on the silicone or alcohol based fluid inside a watertight, yet pressure-sensitive, barrier. This fluid then transmits to the piston or diaphragm.

Why is this important in diving ? First, it prevents salt, sediments and other contaminates from entering the first stage. This reduces internal corrosion and contaminant buildup. Second, it helps isolate the valve mechanism from freezing. This is important if you dive in extreme cold water, like in ice diving. If the first stage does freeze while diving it will seize to work.

Boyle's Law - How Depth Affects Air Volume

diverjamesradio@gmail.com (Diver james) — Sun, 03 Mar 2013 18:04:00 +0000

Sir Robert Boyle was a 17th Century Irish scientist. He wanted to know what happens to a quantity of air if the pressure on it changes. Boyle was greatly influenced by Torricelli. Torricelli determined the pressure exerted by the atmosphere. He determined that the atmosphere pressure equals about 30 inches of mercury.

(Click his picture for more information on GAS laws.)

Boyle has a famous experiment involving a U-shaped glass tube. Here he placed equal amounts of mercury in the tube. One end of the tube was open and the other closed. Under atmosphere pressure the mercury was level and equal. Boyle then started to add mercury to reduce the volume in the closed end. He found that to reduce the volume in the closed end by half, he had to add 30 inches more of mercury. Thus it proved to him that to half the volume in the closed end, a doubling of the atmosphere was needed. In other words, if temperature remains constant, the volume of the gas is inversely proportional to the absolute pressure. If you raise the pressure the volume will decrease proportionately.

Click on pictures to see it better.

Why do I need to know this as a diver ?
The deeper you dive the less volume of air you have in your tank Look at the chart here. Go from 1 ATA( Atmosphere) to 2 ATA you double the ATA but now the tank if 1/2 full. Go to 130 feet or 5 ATA -- 5 times the ATA, but now 1/5 the air volume. Another way. 5 breaths at the surface = to 1 breath at 130 feet. That is pressure and volume relationship. Increase pressure = decrease volume by that amount. This is why your stay at depth is shortened. Click on his picture above for more information on this principle.

Now lets talk about density and pressure. While pressure and volume of a gas are inversely proportional, the pressure and density of a gas are directly proportional. If the gas volume is reduced, the space where the gas molecules are must also be reduced, therefore, the same number of molecules in now a smaller space become compact or denser. Let's get this principle. You reduce the volume (space) by pressure, which reduced the air volume you have to breath. But now the space is smaller for the same number of molecules making them more dense. The relationship is the same as before. If you double the ATA you will double the density because now it is a direct relationship. See chart to help with this relationship. So at depth, you have less air to breath, but the quality of molecules would be increased.

Divers take with them gas-filled containers -Tanks, BCDs, dry suits, mask, - and have have gas filled spaces in their bodies - sinuses, ears, and lungs. Even the tiny bubbles that comprise wet suits continually expand and contract as pressure changes as described by Boyle's Law.

Ascents - 5 Point Procedure

diverjamesradio@gmail.com (Diver james) — Sun, 03 Mar 2013 18:00:00 +0000

A few blogs ago I covered how to do a 5 point and comfortable descents. Now I will cover how to make a 5 point ascent, followed by Part 2 which will be how to ascend safely.

The five points are as follows:

Step 1: SIGNAL BUDDY
As always you and your buddy are diving close to each other. After looking at your SPG (Submersible Pressure Gauge) you have determined that it is time to start to head up. You signal your buddy using your pre-determined signals that you want to go up or need to go up. Your buddy in turns returns the "up" signal. Again, you do this as a buddy team, and only when you are both agreed and facing each other do you start with the next step.

Step 2: NOTE TIME
If you remember from the five point descent, you looked at you watch for the start time of the dive. Now you must again look at your watch for the end bottom time or BT. This is not really your end dive time but for calculating your dive profile using standard dive tables, this is the time that you use. A little confusing ? Let me try to clear it up. The actual dive time for a profile is the start of your descent till the time you start up again. This is of course considered a straight line profile. In other words you are using a standard table and not the PADI wheel. The PADI wheel is used to help calculate multi-level stops along the way up. I may cover this in more details, if I get a question on it.

Step 3: ONE HAND OVER HEAD AND ONE HAND ON BCD CONTROLS
Once you have the time you locate with your left hand the BCD controls, ie, where you will release air. And with your right hand you raise it up over your head. This may seem obvious, but I have seen many divers who do not do this step. You need to have your hand up to make clear the approach to the top.

Step 4: LOOK UP
As you raise your hand up you look up to see where you are going. You want to make sure that you are noting going to hit a boat, or a boat hits you. Although boatings are required to stay a certain distance from divers. Each state has a different distance, so check with the local dive shop to find out. Bare in mind that you are required to dive with a dive flag, so boaters will know where you are. Just a thought for safety. This flag says, "Divers down, stay away". But to be safe, still reach up and look up.

Step 5: SWIM UP SLOWLY BY ROTATING AROUND
Last step is to swim up slowly while turning in a 360 deg rotation. Again, this lets you see all around so if anything is coming from another angle, you will be able to see it.

You are doing all of this while staying as close to your buddy as possible. These are the 5 basic steps to a ascent. On my next blog, I will cover how to make this 5 steps comfortable and how to ascend in a safe manner. I made mention to some of it already.

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Carotid - Sinus Reflex Is this Harmful to Me as a Diver ?

diverjamesradio@gmail.com (Diver james) — Sun, 03 Mar 2013 17:58:00 +0000

How many of you as divers wear tight hoods, or extra tight wet suits, or even tight necks on your dry suit ? If so, have you ever came out of a dive not feeling quite right ? Did you get light headed, or dizzy as a result of it ? I have the answer to why this has happened ?

It is called Carotid-Sinus Reflex. Let's review, as you may know the carotids are the large arteries that run from your heart up the middle part of the neck to the brain.
In fact, these arteries are the major arteries to supply blood, nutrients, and oxygen to the brain. You might remember these as the ones that you check while doing CPR. Oh yea. Thats right. Normally you will sense a pulse while checking during CPR.

Now on to what this reflex is all about. Carotid Sinus receptors monitor blood pressure within these carotid arteries and send impulses to the cardioinhibitory center within the brain to regulate the heart.

So if these sensors senses high blood pressure, it stimulates this center in the brain to slow down the heart. At least till the blood pressure comes down. On the other hand, if these carotid receptors detect low blood pressure, it stops stimulating the cardioinjibitory center, which now in turn stops sending signals to the heart. The heart rate in this case increases.

Now, if a diver wears an excessively tight hood, neck in the wet suit or dry suit that constricts the neck, the carotid sinus receptors incorrectly interprets the excess local pressure as high blood pressure. Which then stimulates the cardioinhibitory center and then slows the heart in responses to it. This slow heart rate slows blood flow to the brain. If the pressure on the neck and receptors continues, causes an even greater high blood pressure, and a continued slow blood flow to the brain. Eventually, a diver may lose consciousness due to the reduced blood supply reaching the brain. In most cases, a diver feels discomfort and light-headedness before the constriction leads to a serious problem.

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Buddy System - What Are The Benefits ?

diverjamesradio@gmail.com (Diver james) — Sat, 02 Mar 2013 17:21:00 +0000

During the confined water and through out your training, using the buddy system is a high priority when you dive. No matter how advanced or skilled you are in diving, you should dive with a buddy. During this topic we will center on why it is important to dive with a buddy.

There are three general reasons to dive with a buddy; they are 1)practicality, 2)safety, and 3) fun. I will talk about each one of these in detail.

1) PRACTICALITY
As mentioned in a previous lesson, having a buddy will help get your gear on. This not only pertains to the BCD, but also the fins, if you are getting them on in the water. They can help stabilize your footing. On the surface you need to conduct the BWRAF procedure. Your buddy helps remind you of your depth, time, to check your air supply.

2) SAFETY
If while diving you do go to deep and begin to 'act" funny, then your buddy and help you up. If you panic and start to breathe fast, they can be there to help calm you down. If you get tired on the surface, they will be able to get you to shore with the tired diver tow. From a safety standpoint, diving with a buddy is a must.

3) FUN
Diving is a social activity. It is something that when a dive is completed, you will be able to talk about for a long time. Together, you and your buddy share experiences and underwater adventures. If you see a "big" fish and tell about it, your dive buddy will agree. Diving with buddies will introduce you to a whole new circle of friends.

Good buddies avoid problems in the following ways:
1) Agree on an entry, exit points, and dive objectives
You need to talk about where you want to go, and what you are trying to accomplish in the dive. Are you going to do a out and back pattern, a square pattern, or random. Talk about who will lead and follow etc. Both buddies show use their compass and track the patterns, so it one is off the other can help.

2) Agree on depth limits and how long the dive will be
This goes along with 1 above. Depends on where you are going.

3) Establish and review communications
Are there different dive signs yo will use. Some common ones are up, down, low on air, directions, check you air, I have ?? psi left. Just go over the signs prior to any dive,

4) Discuss how to stay together, and what to do if separated
If separated, search for 5 minutes and then ascend to the surface, rejoin at the surface, continue dive it air supply warrants it. This is a good practice no matter how deep your dive is.

5) Discuss emergency procedures
Tired diver tows, out of air problems, sharing air. etc.

You and your buddy have a responsibility to each other. For this system to work both of you need to take it serious, but still have fun, while working on staying together. So every dive develop the habit of diving with buddy.

How to Pick the Correct Mask

diverjamesradio@gmail.com (Diver james) — Sat, 02 Mar 2013 17:17:00 +0000

Choosing the right mask is easy. As with most pieces of equipment getting the correct fit is vitally important. A mask that does not fit properly will leak and be uncomfortable, both of these are a constant distraction will diving.

To determine whether a mask will fit or not divers take the following steps.

1. Remove the strap or place it in front of the lens, so it is out of the way.

2. Place the mask lightly against the face while looking up. Make sure the shirt is not tucked under and that the mask is sitting flush to your face.

3. Inhale slightly through your nose. The mask at this point will feel like it is sucking against your face.

4. While inhaling, lightly tuck on the mask and look down. If the mask fits properly, it will remain on you face. If it is loose or falls, then it does not fit your face.

5. Make sure the mask you choose feels comfortable to you. And for all the female divers, it is all about the colors. I know, you need a mask that says something about you, and the color does just that.

Now you need to compare other features. Does the mask have one large lens, or 2 smaller ones? Does it have side lens ? How are the straps, are they easy to use ?

Are you a diver that has glasses. Then you need to get a mask that has 2 lens so that you can buy presciption lens to replace them. Seeing underwater is a good thing.

Why is A Burst Disk Important ?

diverjamesradio@gmail.com (Diver james) — Fri, 01 Mar 2013 15:13:00 +0000

All Scuba cylinders have a maximum working pressure
past which the tank should not be filled too. To help to make certain that the tank doesn't accidentally go beyond this point, some cylinder valves have a device known as a burst disk. This is an industry requirement in North America.

A burst disk consist of a thin copper disk held in place with a gasket and a vented plug. If the pressure inside the tanks rises to 140% of the working pressure, the disk ruptures, and the air escapes thought the vented plug. They are designed to rupture at pressures between 125% and 166%.

Burst disk protect against damage that may occur when the tank is over filled. Burst disk usually rupture when full if they are left to sit in the hot sun. In the hot sun tank pressures have been known to rise to several hundred psi. If the burst disk is old - or the burst disk has the wrong pressure rating - this rise in pressure may be sufficient to cause rupture.

In newer burst disk assemblies the vented plug directs the escaping air to both sides of the valves instead of straight out. This safer because the air escapes won't cause the tank to spin.

Keep in mind, when a tank goes through it's normal yearly Visual Inspection, the burst disk is changed at that time.

Deciphering Cylinder-Neck Hieroglyphics

diverjamesradio@gmail.com (Diver james) — Wed, 20 Feb 2013 14:37:00 +0000

For many divers, the markings around the neck(top) of the tank may well be like reading hieroglyphics. The only real numbers most divers need to know is the tank pressure that the tank will hold, the annual inspection date, and when the periodic tank inspection is due. I will talk about all these as well as the metal types of the of most popular tanks. All dive shop owners will be able to help you interrupt the markings as well as taking care of your tank. Please visit your local dive shop for more information. The marking are not hard to learn and I will attempt to take the mystery out of the markings.

FIRST ROW
GOVERNMENT APPROVAL
First set of letters either DOT or DOT/CTC. These stand for US Department of transportation and the Canadian Transportation Commission. If you travel to Canada and take tanks across the boarder, make sure it has this CTC marking on it. Most tanks sold in the US have the DOT stamp on it.

METAL TYPE
Next set of letters tell what type metal the tank is made from. The 3A denotes carbon steel. Used for early tanks. This tank more prone to corrosion than chrome steel of aluminum.

The 3AA stands for chrome-molybdenum steel. It appears on virtually all steel tanks today.

Aluminum cylinders may bear the designations SP6498, E6498, or most times it is 3AL. First two designations identify permit numbers under which aluminum cylinders are manufactured. But the 3AL is the usual mark you will see on tanks manufactured in the US after July 1, 1982.

WORKING PRESSURE
The next set of numbers, usually four, is the working pressure of the tank. This is expressed in pounds-per-square inch. The cylinder should not be filled past this point. The single exception to this is when you see a + sign at the end of the second row or next to this pressure. That plus sign is usually assigned to steel tank and means you can fill by 10% increase. Most aluminum tanks go to 3000 psi, a few go to 3300 psi. You need to look at this to see what your tank is rated at. Of course the dive shop you take you tanks to will look at this number.

SUBSEQUENT ROWS
SERIAL NUMBERS
Some tanks have a second row while others may have more. All tanks have an unique number assigned to them to identify the tank, this is the serial number. May represent the size and lot number.

MANUFACTURER IDENTIFICATION
This usually follows the serial number and describes the dealer who made the tank. PST is Pressed Steel Company, Luxfer, and Kidde are the common.

HYDROSTATIC DATE
The cylinders initial date follows the manufacturer name. It consist of numbers representing month and year that the cylinder was tested. These numbers will be separated by the hydrostatic tester's initials or a special symbol that the tested had registered with the DOT. Each tank needs to be re-tested every 5 years. Each 5 year test date will appear somewhere at the top around the neck.

This is a brief explanation of tank markings. Like I mentioned above, ask you local dive shop to help you determine what your specific markings mean.

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B.W.R.A.F.-What Does That Mean and Is It Important

diverjamesradio@gmail.com (Diver james) — Sun, 17 Feb 2013 02:20:00 +0000

If you were a pilot getting ready to fly a plane, no matter what size or type, there are certain things you must do before you leave the ground for the 'wide blue yonder'. That one thing is a basic inspection of the plane. They call this a pre-flight inspection. They check the gauges, make sure they have fuel in the wings, make sure all controls are "free and clear." They do this because, if they found something wrong, the pilot or crew could take care of it on the ground better than in the air. Make sense.

As in diving, we have a similar inspection, we call it the BWRAF (Begin With Review And Friend.) I will cover what each letter means and some important points to each. It is important to always dive with a buddy. Your buddy will do this brief inspection on you and then you will return the favor. Your buddy can also help you get your gear on and off. So DIVE WITH A BUDDY.

B - BCD (BUOYANCY COMPENSATION DEVICE)

Make sure that it is the correct size, and that there are no obvious problems with it. Do an over-all look at it. Is it torn in places that cause a problem, does it "just look" safe ? Check the inflators, do they work, both orally and manually.

W - WEIGHTS and WEIGHT SYSTEMS

Did they remember to put them in. You do not want to be in the water and forget your weights. I have seen divers that did it. Is the amount weight they have fit the suit and water they are going to dive. Are you diving with a wet suit or dry suit; fresh water or salt water; it does makes a difference.

R - RELEASES

Do you know where every one is located ? Start at the top and work your way down. They may have a chest strap, belly strap, and cumber bun. Don't forget to look at the weight system they have. Integrated or external ? If they are using a weight belt, do they have a right hand release ? Check them all.

A - AIR SUPPLY

Check the valve to make sure the air is on. There is nothing worse than getting in the water and forgetting to turn your air on. Check your air gauge and make sure you have enough air for the dive you plan to make. Are you making a long, deep dive - get a fresh tank. Short shallow dive may be able to use less than a full tank. But know before you get in the water. Lastly, taste the air to ensure that is it not stale. Put the regulator in your mouth and take a few breathes and taste it.

F - FRIEND - FINAL OK

Do a final look over your buddy's system to ensure that you did not forget anything. That you have all your equipment in place, that nothing is dangling.If all is OK, then give your dive buddy a 'thumbs' up.

After you do this, have your buddy return the favor. This only takes about 5 minutes, but it is time well spent.

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Buoyancy Control - Explain what it is and why it is important when we dive

diverjamesradio@gmail.com (Diver james) — Mon, 11 Feb 2013 02:59:00 +0000

Buoyancy is the force that causes an object to float or sink, and can be described as an upward force exerted on any object placed in a fluid, whether it sinks or floats. Wow, what does that mean ? Means that a force equal to the weight of the fluid displaced by the object. A heavy object will displaced more fluid and sink, while a light object will displace less fluid and rise. This principle is best known as the Archimedes Principle.

With all this being said, there are 3 types of buoyancy. They are positive, negative and neutral buoyancy. If any object weighs less than the water it displaces, we call this positively buoyant. If an object weighs more than the water it displaces, we call this negatively buoyant. And finally, if the object and the water weigh the same, this is neutrally buoyant.

Ascend is the positive side, meaning that you are lighter than the water you displace and you will rise or float. Descend is the negative side where you are heavier than the water and will sink. As divers we need to strive to maintain neutral buoyancy like the diver in the middle.

So as in diving, when we enter the water and we are at the surface we are displaying positive buoyancy. When it is time for us to go under the water, we will become heavier than the water to allow us to be negatively buoyant. Once underwater, and at our depth, we will maintain a neutral state, and hover.

Buoyancy is important for two reasons, one at the surface and one underwater. At the surface we are positive, and we float thereby conserving energy. While underwater we should maintain a neutral position so we can stay off the bottom, and avoid crushing or damaging delicate aquatic life and plants.

Buoyancy control is one of the most important skills you can learn and master as a diver. It is a skill that you will improve on dive after dive. On every dive you must continue to fine tune your buoyancy skills. Good buoyancy skills means that your dive will be fun and effortless.

Lastly, keep in mind salt water verses fresh water has different effects on buoyancy which we will discuss on future lessons. Until next time, "Make Every Dive a Good Dive, and Let's Get Wet."

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What is Refraction and Visual Reversal ?

diverjamesradio@gmail.com (Diver james) — Tue, 23 Jun 2009 14:18:00 +0000

Refraction is the tendency of light to bend as it passes from one medium to another -such as from water to air. It results as light travels at different speeds through various substances due to the different densities.

For example, light travels through air at a faster rate than it does through water, so when light enters the water it enters at a different angle. Unless of course it enters at a pure 90 degree angle, like the sun when it is straight over head.

So for divers to see clearly under water, we wear masks. Now the light must travel from water, glass, and air to reach our eyes. During each pass the light must bend, shape though each medium before we see the object. AS a result objects will appear closer to us at a 4:3 ratio than their actual size. Meaning that an object that is 4 feet away will appear to be only 3 feet away.

There is a tendency to underestimate the distance due to refraction. At greater distances and under certain conditions the objects may appear farther away than this ratio suggests. These phenomenon is called visual reversal, where objecgts appear father away than they actually are.

This reversal depends upon depth and seems to be a result of decreased brightness, and reduced contrast. Also can result from absence of visual / distance cues like what we have on land.
In highly turbid ( low viz ) water, even relatively close objects tend to look farther away.

As a rule and in closing, in estimating distances, the closer the object the more likely it will appear closer than it actually is due to refraction. The more turbid the water, the more likely that close object will appear farther away than it is due to visual reversal.

Evaluation of Dive Conditions

diverjamesradio@gmail.com (Diver james) — Wed, 17 Jun 2009 16:12:00 +0000

If there is a dive planned for a certain location, review and look at the weather forecast for that area of diving and determine before you head out if diving is going to happen or not.

If you live on the coast lines, you may be able to go online and check out surf reports, and tide changes. You would like to dive in an area when you have a slack tide, that is the point between high and low tide. This is where the water has less movement.

Ok now you have determined that the weather is right and the tides are ok. ANd now you are at the site.

PADI trains divers to dive within their training and experience limitations. It is a good idea to check the water conditions once there before you unpack your gear.

When you get there at the site take into account weather at the site, water temperature, bottom composition, waves, depth, local area hazards, and anything else that will have a direct bearing on your dive.

Look for possible entry and exit points and and procedures as part of the pre dive.

At this point decide whether you can make a safe dive.

REMEMBER THIS IS YOUR DECISION - YOU ARE ULTIMATLY RESPONSIBLE FOR YOUR OWN SAFTEY. Only you can make the final decision to dive..

If you do not feel like you can make a safe dive at this site, maybe scrub this site and check put the alternate site.

Diving in poor or potentially dangerous conditions is not fun. You are diving to have fun, adventure, and challenge - not to expose yourself to unreasonable risks.

Nitrogen Narcosis - What Is It ?

diverjamesradio@gmail.com (Diver james) — Wed, 03 Jun 2009 16:16:00 +0000

Deep diving can bring to a diver with another difficulty that relates to nitrogen diving - nitrogen narcosis a euphoric anesthetic effect nicknamed Rapture of the Deep. As you might remember the air we breathe is 21 % Oxygen and 78 % Nitrogen and the other 1% is various gases. On the surface the air gives us no real effects, but at depth and under pressure, nitrogen can give us nitrogen narcosis.

When breathing air nitrogen develops an increase partial pressure at about 100 feet. The exact mechanism surrounding this narcosis is not fully understood, but almost any gas can cause this narcosis under high pressures. Theory suggests that nitrogen becomes dissolved in the lipids(fats) in nerve cells, which interfere with signal transmission from neuron to neuron.

Underwater and at depths reaching 100 feet, nitrogen has a noticeable intoxicating affect that intensifies as you do deeper.

Narcosis may make a diver feel dizzy, sleepy, and may affect memory underwater. They also may feel falsely secure, exercise poor judgement and become uncoordinated.
Nitrogen Narcosis affects divers differently and can affect the same diver differently on different days. It can make a diver feel anxious or uncomfortable, which can lead to panic or other poor decisions.

When you ascend the effects of the narcosis recede quickly , with no after effects. It is not dangerous or harmful in itself, but it impairs judgement and coordination.

This is why divers who do dive deep consistently will dive and be trained to dive with enriched air. This meaning diving with air that is greater than 21% Oxygen. Although diving with increased oxygen can have some for the same effects and carry a different set of risks. This is why a diver must be properly trained in enriched air diving. A topic for future blogs and lessons.

If while diving you start to feel intoxicated, uncoordinated, or confused, immediately ascend to shallower depths to relieve the feeling. If your buddy acts impaired help him to a shallower depth.

To prevent Nitrogen Narcosis, simply avoid deep dives. Take and be trained in the Padi Deep Dive Certification Course. In this the instructors can watch and observe you under water and at depth.

What Is An SPG ?

diverjamesradio@gmail.com (Diver james) — Sun, 31 May 2009 12:12:00 +0000

First off the SPG stands for Submersible Pressure Guage. SPGs let divers monitor their air supply (pressure) throughout the course of the dive. Such guages connect to the high pressure port on the regulator's first stage. Click on picture to take you to Leisure Pro Equipment.

You will learn to use the SPG to plan and control your dive so you return safely to the boat or shore without running out of air. The SPG is considered mandatory equipment when you dive, that is if you do not dive with a computer. Depending on the dive and type of dive, some divers dive with both an SPG and computer. The SPG of course is th back up.

A vital point to remember, that the SPG is a passive device. You have to read it, or it doesn't do any good. Develop the habit of looking at it frequently through out out the dive. When you dive alot you can get the feel of how fast you breathe air, and know about when you are to run out. So you may not need to check that often. But for the new divers, I recommend checking it often. Better too much than too little.

The most common type is an analog model with a spiral wound bourbon tube. Europeans SPGs go to 300 bar, while in North America SPGs range from 3500 - 4000 psi. On the dial the SPGs are color coded. In Europe for 0-35-70 bar and North America 500- 000 psi. The color is usually red and warns that you are dangerous low on air and need to return to surface immediately.

How to Determine the Proper Amount of Weight Needed for the Dive

diverjamesradio@gmail.com (Diver james) — Wed, 27 May 2009 14:16:00 +0000

Divers take the weight belt and systems for granted more than they should.
This is the system that allows them to have a safe and comfortable dive. Too much weight and you are always struggling to maintain buoynancy, too little weight and the descent to start the dive will be difficult.

HOW MUCH WEIGHT IS ENOUGH ?

Before going on the first dive, we teach divers to do the weight and buoyancy test. This is how the test is performed. You will have to enlist the help of other divers to help with this test. You will start off with some weight in the BCD. Thew dive shop or instructor will give you a basic guide to how much. This depends on a few factors: what type water you are diveing be it salt or fresh water, also how much weight you are. Are you thin, heavy, or in between. Keep in mind that this is a starting weight.

To do the test. You will need to enlist the help of other divers to hand you weight etc.

1. Enter the water with all the gear and your estimated weight. Get in water that is over your head but not far from the exit and shore.

2. Make sure that all the air is out of the BCD. Keep the regulator in your mouth, and hold a NORMAL breath of air. Be ready to kick up if you begin to sink. This is where the help is needed.

4. You should float at eye level. If you do not, add or suntract weight till you are. You can just hold the weights till you figure out how much. Then once you do you can intergrate them into your BCD or Weight belt.

5. As a final check, exhale. You should begin to slowly descend if you have the proper amount of weight. You should also raise the deflator over your head with your left hand. This will also help you decend, because now you are using the weight of you arm to help with this.

6. Once you have dtermined the weight to this point, you will need to add a small amount ot EXTRA weight (about 2 pounds)

Why ? Air has weight. As you use the air in your tank the tank begins to become lighter and more buoyant. Add ting extra weight will off set the buoynacy factor that you get by the end of the dive.

HOW DOES THE WEIGHT AFFECT MY DIVE UNDERWATER ?

Weight also has a direct effect on how often bouyanct adjustments are made. If the diver carries more weight than needed to "help get underwater better". they also have to add more air to the BCD as they dive to ofset the extra lead weight added on the surface. Now the volume of air exchanges with depth, this causes a greater changes in buoyancy, which causes a diver to adjust the air in their BCDs more often.

Factors Predisposing Divers to Decompression Sickness

diverjamesradio@gmail.com (Diver james) — Wed, 20 May 2009 14:03:00 +0000

As mentioned in the last blog and talkcast, the way to avoid is to limit the factors that predispose divers to DCS. Some factors are unavoidable. So make the others of more importance. Physiologists still don't understand all factors that may predispose an individual to DCS, but the list is a start to what they do know. No matter what you do, DIVE CONSERVATIVELY. NEVER DIVE TO THE LIMITS OF A DIVE TABLE OR COMPUTER. They may be wrong for you at that time.

Following is a short list of these factors and a brief explanation.

FAT TISSUE

Fat tissue is slow tissue, holding a high amount of dissolved nitrogen. A lot of fat tissue increases the nitrogen retained in the body. Divers that have a higher fat ratio to lean muscle are more likely to have more nitrogen after a dive and therefore have a slightly higher risk of DCS.

AGE

The circulatory and respiratory system works less efficiently in the older population. This interferes with gas exchange. Remain fit by reducing the fat content and exercising regularly to counter this factor.

DEHYDRATION

Dehydration reduces the quanity (volume) of blood available for gas exchange, slowing nitrogen removal from the body. Comsumption of diuretics (caffine), profuse perspiration, and even the dry scuba air tend to dehydrate the diver. During metabolism of alcohol uses a great deal of water. Thus a diver with a hangover is more likely to be partially dehydrated. To do: Make sure you drink plenty of water before, during and after the dive. More than you normally would do.

INJURIES AND ILLNESS

Any condition that affects normal circulation can potentially affect nitrogen elimination. Healed conditions may reduce local circulation difficulties. Also any illness can produce a general reduction in circulation. Make sure you do not dive if you have any injuries or illnesses. It is simply not worth it. Better to heal and dive a different day.

ALCOHOL

Alcohol consumed before or after a dive alters physiology, we all know that but in favor of DCS. Alcohol tends to accelerate circulation and can cause tissues to carry higher amounts of nitrogen. After a dive, alcohol dilates capillaries, possibly increasing the rate of nitrogen release and bubble formation.

CARBON DIOXIDE

Elevated carbon dioxide from skip breathing or improper breathing may interfere with the gas transport by the circulatory system by dilating the capillaries, and again increasing nitrogen uptake.

COLD WATER

During a cold dive, inadequate exposure protection in moderately warm water, changes normal circulation, as the body trys to stay warm. At start of dive, circulation carries nitrogen to all parts of the body, but as heat is conserved, this reduces circulation to the hands and feet. There is less blood to carry away dissolved nitrogen during ascent.

HEAVY EXERCISE

Exercise while diving increases blood circulation, carrying nitrogen to all parts of the body faster than normal. After resting, circulation returns to normal, and so there is no corresponding circulation to accelerate nitrogen elimination.

ALTITUDE AND FLYING AFTER A DIVE

Reduced atmosphere pressure at altitude increases the pressure gradient between tissue and the ambient pressures and can possibly cause larger bubble formation. Once DCS occurs returning to sea level does not usually correct the problem

The Squeeze is On

diverjamesradio@gmail.com (Diver james) — Sun, 17 May 2009 22:56:00 +0000

What do I mean by this statement ? As divers, we have many areas that can cause us to have equipment squeezes. But one of the main areas that affect most of us as divers is the squeeze that occurs from our face mask.

Unequalized air spaces can create problems. As mention the mask squeeze is common and occurs on very rapid descents when the diver neglects to equalize the mask.
Increasing hydrostatic pressure forces tissues surrounding the eye to swell into the uncompensated air spaces to fill the reduced air volume.

This swelling damages the capillaries, bruising the skin around the eyes and cheeks. Mask squeeze looks dramatic and severe, and the diver may not know it happened until they look in the mirror. This squeeze clears without complications, but the victim may want to consult an MD.

Other squeeze that may occur is when a diver uses a dry suit. If the diver forgets to add air to the suit and ignores the pinching, and continues to descend, may cause welts and injury.

During ascents the diver must remember to release the air from the suit, or risk a possible runaway ascent.

The Difference Between DCS and DCI

diverjamesradio@gmail.com (Diver james) — Mon, 11 May 2009 00:58:00 +0000

Most divers do not know there is a difference between Decompression Sickness (DCS) and Decompression Illness (DCI). There is a large difference.

First we must define what we mean by DCS. There is an overall term called Decompression Illness (DCI) which most divers get confused and call decompression sickness (DCS), the same. No it is not the same. DCI is the over all term that has 2 subjects below it: 1) DCS and 2) Lung Over expansion Injuries.

DCS refers to the conditions caused by inert nitrogen gas coming out of solution within the body. Lung Over expansion Injuries refer to those injuries that are caused by holding your breath on ascent.

There are basically 2 types of DCS: Type I deal with skin and pain only which would include the sub type a) Cutaneous DCS and b) Joint and limb pain DCS. While Type II covers the more life-threatening which are the c) neurological DCS and d) Pulmonary DCS.

A) CUTANEOUS DECOMPRESSION SICKNESS

Bubbles coming out of solution in skin capillaries can cause this type.

B) JOINT AND LIMB PAIN DECOMPRESSION SICKNESS

Bubbles growing around and inside the tendons, ligaments and related muscles are the immediate cause. Symptoms may be found in one place on the same limb or bilateral symptoms. This type may be serious because it can lead to a mores serious problem.

C) NEUROLOGICAL DECOMPRESSION SICKNESS

Effects on the nervous system produce some of the more serious cases in DCS. Bubbles in the nervous tissue may block blood flow "backing up" the system and reduce arterial flow in the affected areas. This affects the spinal cord most often often causing numbness and paralysis in the lower legs. It tend creeps upwards to affect from the neck down.

D) PULMONARY DECOMPRESSION SICKNESS

This is DCS that manifesting itself in the lung capillaries resulting in the onset of life-threatening symptoms. Silent bubbles reach the pulmonary capilaries defusing into the alveoli. In some cases, bubbles accumulate faster than they diffuse and can block and back up blood flow to the lungs. With less blood flowing to the lungs, the left side of the heart gets less blood, causing the heart rate to rise and a drop in blood pressure. With no treatment, the circulatory system may fail.

There are four type of Lung Overexpansion Injuries

A) AIR EMBOLISM

This is if air enters the bloodstream through a ruptured alveoli into the pulmonary capillaries.

B) PNEUMOTHORAX

If lung over pressurized tears at the surface, the expanding air leaks between the lung and the peural lining.

C) MEDIASTINAL EMPHYSEMA

This is where air accumulates in the mediastinum.

D) SUBCUTANEOUS EMPHYSEMA

Follows that of Mediastinal Emphysema as air seeks its way from the mediastinum, foloowing the path of least resistance into the soft tissues at the base of the neck.

What is the Difference between Steel and Aluminum Tanks ?

diverjamesradio@gmail.com (Diver james) — Sun, 03 May 2009 18:27:00 +0000

During this blog I am going to explain the differences between a steel tank and an aluminum tank.

There are many pros and cons concerning which tank you dive with, I will try to highlight those differences do when you do decide on buying a set of tanks, you will be better informed. Of course, as always, consult you local dive shop so you can see and touch the tanks you are considering buying. They will be able to fill in the blanks for you concerning which to buy and why. I hope that this information is helpful. Now let's get on with it.

The vast majority of tanks today are either steel or aluminum.

STEEL

Most are made from chrome-molybdenum steel. Steel cylinders are hard and therefore resistant to external damage. The draw back for steel, without proper care, they may rust (A chemical reaction that forms iron oxide), not only on the outside, but inside as well. One reason to have your tanks visually inspected every year. Highly recommended.

ALUMINUM

Softer than steel, ie can become damaged for external forces. Because of this, the walls are thicker. This makes them larger, heavier, and more positively buoyant than steel. Like steel aluminum also corrodes forming aluminum oxide. Unlike the iron oxide, it actually inhibits further corrosion.

SIZE AND WEIGHT

Aluminum weighs less than steel. Because they are not as strong, tend to be larger and heavier than steel. This can concern the smaller diver.

BUOYANCY

Because aluminum is larger they displace more water and often times more buoyant. As such divers will need more weight in their belt for a diver. At the end of the dive they tend to be more positively buoyant. Where as steel is negatively buoyant after a dive. The total difference can be 4-8 pounds.

VALVE TYPES

Most steel tanks are considered high pressure tanks, which mean that they may have the plus sign after the tank allowed pressure. This as you remember means that you can fill it up to 10 % higher than what is listed. Most steel tanks have what you call a DIN valve, where the first stage of your regulator screws into the tank. This tends to get a more secure fit. While the aluminum tanks have a K valve, where the first stage just rest against the tank stem, and is held in place by sir pressure.

COST

Steel tanks cost considerably more than aluminum.

Wreck Diving Certification

diverjamesradio@gmail.com (Diver james) — Wed, 29 Apr 2009 17:33:00 +0000

If you go to my blog on Scuba Diving - Learn to Dive Safe, you will see I have done 3 basic classes on Wreck diving. How to Evaluate, navigate, map, penetrate, and special considerations. Todays class in just on what doe it take to be a certified wreck diver for PADI.

As with most PADI classes you will get your course book with the associated DVD. It would be wise to read the text, watch the DVD, and do the required knowledge reviews before you do the dives. Some shops will have a brief class to discuss the material and go over the answers to the reviews.

After the book work it is time to do the required dives, There are 3 dives that must be completed prior to certification. I will go through each dive briefly.

DIVE 1

This dive could be part of the Advanced dive certification. On this dive, you simply will dive on the wreck and do an overview, This will be on the exterior of the wreck. Get the general feel of the wreck, how is it sitting, and where are the hazards. In other words, just have fun diving a wreck. Watch the aquatic life that lives there. During this dive practice avoiding silting. Learn to navigate on a wreck by following the wrecks features (layout), feature references, and base line references.

DIVE 2

Now we start to do some work on this dive. Go to my blog on Scuba diving yo learn more about this. On this dive you will navigate and map the wreck. Look to areas that you can penetrate later. Assess for stability. Look for possible hazards, points of interest, and general condition. Two Benefits to map a wreck are to simiply future dives and to help plan for a possible penetration of the wreck.

DIVE 3

First you will practice how to use the penetration line on the surface. Then when you do the dive you will use the penetration lines along the outside of the wreck. This way you see how to handle the lines underwater. Swim out from the wreck and use the line as a retrieval line. Swim along the lines using your lights. Need to see how you handle all the gear at one time.

DIVE 4

This dive can either be a tour wreck dive or a penetration dive. Some wrecks you dive on can not be penetrated. So you do not need to penetrate to get the certification. But It is nice if you could penetrate a wreck under the supervision of an instructor.

You need to learn how to avoid the 5 hazards of a wreck: This is why special wreck training in essential:
1. Loss of direction
2. No direct access to the surface
3. Restricted passages
4. Falling objects
5. Silt

Once you have completed all 4 dives, and the knowledge reviews, then you will awarded the Wreck Diver Certification.

What is the Difference Between Freshwater and Saltwater ?

diverjamesradio@gmail.com (Diver james) — Sun, 26 Apr 2009 04:56:00 +0000

Most people other than divers think there is a no difference between salt and fresh water.
As a diver you need to understand the difference and account for it when you change from one type water to the other. There are certain environments that tell you if a body of water is salt or fresh. Before you go on a dive, or trip, you need to find out and ask what the water is. You need to put this information into account as you make your planning. (Click on Picture to link to Phuket, Thailand diving - Great place to dive.)

FRESHWATER

Freshwater sites are lakes, quarries, springs, and rivers. Many of these require special training before you participate in them. Many also may be in the higher altitudes, again, you need special training to dive in higher altitudes.

Remember that in freshwater you need to consider currents, bottom compositions, limited visibility, thermoclines, cold water and entanglements.

SALTWATER

Saltwater sites include for the most part oceans. These fit into 3 general classifications according to temperatures: temperate, tropical, and polar. The vast majority fits into temperate and tropical.

General considerations for these environments include waves, surf, currents, coral, boats, deep water, marine life and remote locations.

Enough about definitions and types, how does it effect me as a diver ? It has to do with buoyancy. First off fressh water weight less per cu foot than salt water. Just for referenec: freshwater weighs 62.4 pounds / cu foot, and saltwater weighs 64.0 pounds / cu foot. Ok , so.

Since freshwater weighs less than saltwater, you're not as buoyant for a given displacement. This means that if you dive in freshwater after you dive in saltwater, assuming you dive in the same gear and exposure suit, you'll need less weight.

So lets say in saltwater you dive with suit etc, and 15 pounds of extra weights than you go to do a dive in freshwater, you might be albe to do it with 8 - 10 pounds. Just remember that if you go from fresshwater to saltwater you will need to add on weight, from saltwater to freshwater, you will take some weight off.

The amount of weight to adjust will be based on experience in the water as far as comfort, the amount of salt in the water, and how you are breathing underwater that day. Just keep in mind that there is a difference between the weight you use in freshwater and saltwater are different.

What is AOWD ?

diverjamesradio@gmail.com (Diver james) — Thu, 09 Apr 2009 01:46:00 +0000

Simply put AOWD stands for Advanced Open Water Diver. What is this rating according to PADI ?

After the basic Open Water training the next logical step is to get the Advanced Open Water Diver certification. This rating consist of 5 dives that may span over two days or could be in 5 separate days. Basically you look at all the advanced specialties that PADI offers, and you are going to make the first dive of these specialties in 5 of them. However there is an exception. You must make the deep dive and the navigation dive as 2 of the dives. The other three can be a choice from a wide list of dives. Some of the choices are as follows: Altitude, wreck, night, dry suit, photography, search and recovery, drift, DPV (Dive Propulsion Vehicle), Enriched air, PPB (Peak Positive Buoyancy) and Boat just to name a few.

Once you have picked your 5 dives you must complete the text readings, and knowledge reviews in them. The advanced book will have all the other dives listed as well, you are only responsible for the 5 dives you pick.

Once you have done your 5 dives, the readings, and knowledge reviews you will awarded the Advanced Open Water Diver Certification card (or C-card).

But why do I need this certification. Remember I said you need to do the deep and navigation dives as part of you 5 total dives. The reason stems around those dives.

When you go on a dive trip, the DM(Dive Master) of the boat will ask for C Cards. If you have the Advanced Card they know you have had training in diving deep and navigation. Most dive operations take divers to spots that have the potential for a deep dive. If you had the training they know that they do not have to worry about your going deep and hurting yourself. They know you had the training.

Now for Navigation. In the Open water course we teach you to use a compass on the surface and underwater in a straight line. In this dive, we will teach you how to do a square, and a tri-angle. Every dive you do will have in it some form of navigation skills. Every diver need more advanced training in this area, and what you learn in the advanced course is that more advanced training. Not the end all to navigation, but a start.

Once these 5 dives are completed, you will be given credit for the first dive if you chose to go on and complete the entire specialty rating for those dives, Which I highly recommend.

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