Tuesday, June 23, 2009

What is Refraction and Visual Reversal ?

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.

Wednesday, June 17, 2009

Evaluation of Dive Conditions

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.


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.

Wednesday, June 3, 2009

Nitrogen Narcosis - What Is It ?

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.

Sunday, May 31, 2009

What Is An SPG ?

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.

Wednesday, May 27, 2009

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

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.


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.


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.

Wednesday, May 20, 2009

Factors Predisposing Divers
to Decompression Sickness

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 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.


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 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.


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 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.


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.


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.


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.


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

Sunday, May 17, 2009

The Squeeze is On

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.

Sunday, May 10, 2009

The Difference Between DCS and DCI

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.


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


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.


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.


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


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


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


This is where air accumulates in the mediastinum.


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.

Sunday, May 3, 2009

What is the Difference between
Steel and Aluminum Tanks ?

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.


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.


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.


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.


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.


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.


Steel tanks cost considerably more than aluminum.

Wednesday, April 29, 2009

Wreck Diving Certification

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.


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.


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.


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.


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.

Saturday, April 25, 2009

What is the Difference Between
Freshwater and Saltwater ?

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 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 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.

Wednesday, April 8, 2009

What is AOWD ?

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.

Check out my sponsors links for soem FREE items.

Tuesday, April 7, 2009

Wreck Diving Limits -
Are You Diving to the Limits ?

When we talk about penetrating a wreck we, as divers, are always interested in the light we will have inside. Some of the light comes from the surface in the form of ambient (sun) light, while we provide other light from the dive lights we carry. Remember you should always carry one primary and at least 1, of possible 2 back up lights. The more backup lights the better.

During this blog we will talk about the limits established for diving in overhead environments. Here we are talking about a wreck, but it could, and does cross over to diving in a cave. In the near future I will have on my talkshoe show # 20348, Ron Carmichael who is an expert in training divers to dive in a cave. Look for dates of that interview in an upcoming blog and talkcast.

There are at least three limits we must observe.

1. Edge of light zone
When you enter the wreck and look back you will see some light, that is the ambient light coming from the surface/ Stay within this light that is available. Meaning that you should not penetrate if you can no longer see this light. If the dive is murky, then there will be less natural light entering the wreck. This also means, of course, that you should not make a penetration dive at night.

2. Linear distances of 40 meters /130 feet
In open water per PADI guidelines, a diver should not dive deeper than 40 meters / 130 feet. This is of course the recreational safe limits. There are courses that teach divers to dive deeper, but only attempt that under a certified instructor. Similarly, your maximum distance from the surface when penetrating a wreck should not exceed this same distance. This means that the depth of the wreck and penetration distance should not exceed 130 feet.

3. One third of your air supply
Whenever you dive in an overhead environment you dive and exit the wreck with 2/3 air and this includes the time it takes to surface. Simply put it this way, 1/3 to dive and go into the wreck, 1/3 to exit and go to the surface and 1/3 reserve.

This is known as the "Rule of Thirds". Saving two thirds of your air for exiting gives you more than of the most important factor you need to handle a problem inside a wreck: time.

You do not have to surface with 1/3 air, just exit the wreck with the air. You can dive around the wreck till an appropriate time to surface as you would if in open water. If diving deep, make sure you give yourself time to do a 15 feet stop for 3 minutes, ie a safety stop.

Monday, April 6, 2009

How To Handle STRESS Underwater

When you dive do you ever get Stressed ?
What steps can I take as a diver to help with underwater diver stress. When you encounter a potentially seious problem - whether your own problem or someone else's. There are four things to do to help with this problem.

Whatever caused this stress, just stop what you are doing. If you need to hold onto a rock, or plant your hand in the sand, do it. Just stop swimming. Remain still, conserve energy. If your stress is due to an increased breathing rate then stoppinmg is a good thing to do. Read my last blog on hypercapnia, and the first cause of that condition. Stopping is good.

Just breathe normally, concentrate on breathing in deep and slow. Remember that no matter what caused the stress, you still have air in your tank, and all is OK. This helps calm you so you can think clearly. If your buddy is breathing fast help him getr control of his rate. Stop, above, will help with this as well.

Think of the most direct, simple way to solve and overcome the problem.
If it was your breathing rate, then you have this under control. Are you tangled in lines or a fishing net ? What is the best way to cut free. Don't panic, all is ok.

4. ACT
Put into action the steps you thought through.

If the above does not relieve the situation after one or two tries. start over: stop, breathe, think and act.

These 4 steps seem like they may take along time to perform, where in reality, will only take a few minutes. More importantly, by training yourself to follow these steps, you avoid blind instinctive reactions that often lead to ineffective results. Through practice and training and by mentally rehearsing how to respond in various situations, you'll be able to act correctly, decisively, and calmly when facing a problem.

Thursday, April 2, 2009

Hypercapnia - Are You Diving High ?

Hypercapnia .... that sounds pretty serious. Yes it can be. Let's first define what this is and I will try to explain it. Definition: (also called hypercarbia) or excess carbon dioxide, can result from many causes. I will explain each to these.


Most common cause when a diver fails to breath slow and deep. If he does then you have small tidal volume (amount of air inhaled and exhaled during normal breathing), and high proportion of dead air to fresh air in the alveoli. Carbon dioxide levels in the alveoli and bloodstream increase, causing headaches, confusion, and a further accelerated breathing until the divers slows down and resumes deep, slow breathes. If unchecked, this elevated increase in carbon dioxide can lead to loss of consciousness.

In closed and semi-closed scuba gear, ( rebreaters ) and full face mask, have been associated with hypercapnia due to large dead air space (portion of divers tidal volume that plays no direct part in air / gas exchange.) However, in open circuit scuba used in recreational diving, hypercapnia due to dead air space is rare, but can happen.


If diver attempts heavy work underwater, muscle tissues can produce carbon dioxide faster than the respiratory system can eliminate it. This increase in carbon dioxide causes the respiratory center to stimulate a higher breathing rate to get rid of this increase. Because of the denser air breathed at depth, this requires more effort by the diaphragm and other muscles to overcome resistance from turbulence. This additional effort furture increases carbon dioxide production, resulting in yet a higher demand for increased breathing. This cycle continues until the diver slows down or stops activity, after which, the respiratory system catches up with the body gas-exchange needs.


This is holding your breath while scuba diving in order to extend your air supply. In reality, this techniques leads to an increase in carbon dioxide in their circulatory system, until it actually stimulates faster breathing and therefore helps to deplete air supply faster.


Contaminated air is rare in recreational diving. But it is always a good idea to breathe from your regulator prior to the dive to ensure the air taste "fresh". Part of the BWRAF procedure. The symptoms are the same as for improper breathing.

Bottom line: Breathe at a slow, deep, and unlabored rate. This will keep you safe, and allow you more "air" time underwater.

Wednesday, April 1, 2009

Responsible Diver Checklist

When you drive a car, there are certain things you must do to be considered a responsible driver. Just like in driving there also things we must do to be considered a responsible diver. The saying "ENJOY THE DIVE" will help you remember it.

E - Equipment well maintained and complete
Are you diving with old equipment ? When was your equipment last inspected and serviced ? You should have all equipment serviced on a yearly basis. The regulator needs to have all seals, and parts replaced every year. If you own tanks, again they need to be visually inspected yearly. They will drain all the air out, and look inside. Check the seals and refill. Has it been 5 years since you had the tank, you may need it to be hydro-tested.

N - Neutrally buoyant at all times
While at depth, you need to make sure that you are neutral to help protect the coral, plant life, and fish. Make sure your weights are positioned correctly to maintain a horizonatal position.

J - Just say no to drugs and alcohol
Goes with out saying, drugs and alcohol are not a good thing to do. It is even bad while diving. We, as divers, do not say we can not drink. But if you do drink then the last dive you made that day WAS your last dive. Alcohol predisposes you to DCS (decompression Sickness)

O - Observe conditions before the dive
What is the weather like the day of your dive ? What is the surf, or water conditions ? One of the hardest choices a diver has to make is whether to "dive or not dive". There is always the next day. Why put yourself in a potentially harmful position by diving in bad conditions, especially if they are beyond your training experience. Just stay out if you ever have a question on it.

Y - You've checked your air supply
Again another no brainer. Do the BWRAF procedure and check the air supply. Make sure you have enough for the dive and the air is turned on.

T - Take a safety stop before surfacing
Make a recommended stop at 15 feet for 3 minutes. This gives your body more time to "off gas" nitrogen before you exit.

H - Have an alternate air source
Must at least have an octopus set up in the "triangle" area. But better yet you should consider having a redundant air supply. An extra air supply with enough air to get you to the surface from any depth. My choice would be Spare Air. Check them out.

E - Enter and exit with care
You have a lot of gear on, so make sure you watch where you are walking. You do not want to fall and injure yourself before you get to the water. Pick good enter and exit points that are easy to navigate from keeping in mine safety.

D - Dive your plan
Every dive you go should be planned. The maximun depth, time, how you will swim the dive, who will lead, etc. Go over signals prior to the dive. Go over what you want to accomplish on the dive, ie see the wreck, feed the fish. Do not alter your dive plan, while underwater you may be thinking clearly and to alter it then, might put you and your buddy in an unsafe condition. Try to stay close to the plan you set.

I - I am a Responsible Diver
Make this statement to yourself that you are responsible and that you WILL do things to make you a responsible diver. Reading this is the first step towards that goal. Good for you.

V - Verify your buddy's equipment
Go over you buddys equipment prior to the dive by doing the BWRAF procedure. Check to make sure it is complete and working properly.

E - Enjoy the dive !
Above all this, make sure you enjoy the dive. The best way to do this is to make sure that you are properly trained for the dive you will make, that you have had plenty of rest prior to the dive, that you are mentally ready, and that you have planned the dive. If you do all the above you will have a Great dive.

Lets all be Responsible Divers. Until next time "Let's Get Wet".

Tuesday, March 31, 2009

Ascents - Comfortable Ascents -
Are You a S.A.F.E. Diver ?

First off I must ask "What is the most important rule in scuba diving ? That's right. Breathe continuously and never hold your breath while using scuba. We teach you this in the basic course and watch you often to see if there is bubbles coming from your regulator. We may even point to our mouths to remind you to do it underwater. There are some divers who do it while at depth to conserve air. This is know as skip breathing, not a good thing to do at depth. There are better ways to increase air time underwater, which I may cover in a later blog.

Why is this rule important ? For one, If you hold your breathe while ascending you could die. But why ? What happens ? If you hold your breath you create a "closed bag" if I may with your lungs. No place for air to go. As you ascend your lungs will increase in size by nature of the ascent. You could get a lung rupture as a result. This rupture forces bubbles into the bloodstream, blocking blood flow to the brain and other parts of your body, leading to paralysis, serious injury, or death. If you hold your breath for even 1 meter or a few feet, your lungs could over expand, just like the small bag.

If you feel discomfort in your ears while ascending, stop, go down a few feet and wait for it to clear. Afterwards, continue to ascend. Remember it is never a good idea to dive while having a cold, and on decongestants. They could wear off, trapping air in the ears and sinuses. If they do wear off you could get a "reverse Block."

Now the S.A.F.E. part. This stands for Slowly Ascend From Every Dive.
This is really the PADI motto, so to speak. But how ? The rate of ascent should be no faster than 60 feet per minute, but slower is better. Your body needs time to adjust to the changing pressures, time to regulate your buoyancy, keep track of your buddy, and to watch for obstructions.

The best way to ascend is to use a dive line if diving from a boat, or follow the bottom contour, to make a slow trip to the surface. Make sure you start up with plenty of air.

One last note, it is always a good idea to stop your ascent at 15 feet for 3 minutes, again to offset more pressure gases. This is known as a safety stop..

Think of the 60 feet per minute as a speed limit. It is fine to go slower, slower is better. Be a S.A.F.E. diver: Slowly Ascend From Every dive

Wednesday, March 25, 2009

Descents - Comfortable Descent

In my last lesson, a discussion was made on how to do the 5 point descent. Let's do a quick review, 1) signal your buddy you are ready to "go down" with the OK sign, 2)look for a reference point for your location, 3) look at your dive watch for the start time of the dive (very important if you are not using a dive computer), 4) do a snorkel and regulator exchange, 5) lift the manual inflator from your BCD and deflate the air. This will allow you to be heavier than the water you displace (negatively buoyant) causing you to sink below the surface. From this point we will talk about how to do a comfortable descent.

As soon as your head goes under water you should equalize your ears. There are many ways to equalize your ears.

1. Equalize your ears early and often as you descent, every few feet. Don't wait for discomfort, that is too late. If you equalize often, you shouldn't feel discomfort.

2. Block your nose and gently blow through it. If you blow too hard, damage could result to your ear drums. This will not only end your dive, but could take months to heal. So, "gently" blow through your nose.

3. Swallow and wiggle your jaw from side to side.

4. Could do both of the above at the same time.

5. One thing that helps me at times is to lean my head to the side of the blocked ear, while pulling on my ear. This "loosens" up the space and may allow the pressures to become equal.

6. Add air to your mask through your nose. This prevents uncomfortable mask squeeze. In fact, you should do this procedure many times while at depth. This also helps keep water out of the bottom of the mask.

There are a few procedures you can do should you feel discomfort.
Ascend up a few feet till you feel no discomfort. At this depth, gently try to equalize your blocked ear. If you air space equalizes continue diving to depth while continueing the procedure. If you can not equalize, discontinue the dive. Signal your Divemaster or buddys that you are having ear problems and must ascend, and end the dive.

If you have cold, allergy or other congestion problems will cause you to have trouble equalizing your ears. Blocking off the air space with ears plugs or a tight fitting hood can cause problems. If your are wearing tight hood, as you descend reach in and allow some water to enter, this will prevent this from being the problem. I do not recommend diving while taking cold medications. If during the dive the medications wear off, you may have what we call a "reverse block". This is where you have a ear/air block on the ascent. Not a good thing. You need to exit the water, and the futher up you go causes more pain. So if you have cold, allergy....DO NOT DIVE AND DO NOT TAKE MEDICATIONS FOR IT WHILE DIVING.

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Sunday, March 22, 2009

Descents - 5 Point Procedure

In order to make a comfortable decent there are a few things you need to do first. You and your buddy need to put together your equipment and preform the pre-dive safety procedure B.W.R.A.F. Once that is completed, enter the water and put air into your BCD to about 1/4 fill, or just enough to keep your head above water. Do not over fill your BCD. Next, put in your snorkel in your mouth, it should come from the left side, while the regulator comes from the right. Swim to your desired dive spot, doing a snorkel swim. At this point, if you use your regulator you will be using precious air that you could be using while under water. Conserve your air.
Once at your site, the 5 point procedure begins.

Step 1: OK
While facing your buddy, give the OK to go down and start the dive. You and your buddy need to agree to "go down". This first step insures that both of you are ready to begin the dive, and insures both are on the "same page".

This simply means that you pick out a point somewhere on shore, or a anchored boat. By doing this you start out having a reference point. If you make a straight down descent, once on the bottom and at depth you know which direction the reference is. This, of course, is based on a non-compass dive, which I DO NOT recommend. You need to learn how to use the compass, and always dive with one. Trust me, you NEED the Compass.

Step 3: TIME
Take a look at your watch and make a mental note of the time. This time is what you will use to calculate your final dive profile. Later I will go over how to calculate a diver profile, but for now a time is defined as the start of the descent to the start of the ascent. Like I said this start time is important for this reason.

At this point you have your snorkel in your mouth, and need to remove it and place in your regulator. You do this by holding the snorkel in your left hand while the regulator is in your right. Now, take out the snorkel and place in your regulator. Make sure you clear your regulator of water before breathing thought it.

With your left hand place it on the manual inflator button. Raise it above your head, so as gravity and water puts a force on the BCD which allows air to be released. This makes you negatively buoyant, because now you weigh heavier than the water you displace, and therefore you sink.

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