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How Things Work – The Scuba Air Delivery System

April 19, 2011 By nigellakey Leave a Comment

Earlier, I wrote about the need to properly maintain your BCD. It is a crucial part of our portable life support system that we carry with us when we enter the strange and magical underwater world. While each element of our dive system is important to having a safe and enjoyable dive, there is no component more important that our air delivery system- it is at the pinnacle of our portable life support system hierarchy. It delivers breathing gas to us in an environment that would otherwise be hostile, and yet despite its importance, like most other parts of our dive system it goes about its business unheralded, without complaint and typically, almost entirely unnoticed.

Think about that for a moment- except for brief moments when the mouthpiece is uncomfortable or we have a free-flow that startles us, the air delivery system fades into the background, and we instead focus on the fins that are too tight or the mask that hurts our nose. The truth seems to be that the air delivery system simply, well…works. It delivers breathing gas to us when we want it, seemingly no matter what else is going on during our dive. I think that’s a really good thing- a piece of equipment so critical to our survival, often ignored, and yet it keeps on doing its job dive after dive. It should go without saying that since the air delivery system is a piece of life support equipment, it’s not a place to scrimp. Further, it is one of the parts of a dive system that you really should own.

Years ago, back when we still had coal-burning wristwatches and communications devices called “letters” were actually written using your hands, the air delivery system was, to be kind, primitive and less, can we say, reliable. My aim here is not to discuss the evolution of the technology, but rather to explain how these things work, in practical terms. My discussion will be limited to the typical, open circuit demand systems, which we usually refer to as our “regulator.” Also, while you can find extremely detailed explanations, including the physics, concerning the operation of air delivery systems, I’ll restrict this piece to a functional overview.

In reality, the air delivery system does regulate, so that’s not truly a misnomer. However, despite the device’s purpose of regulating the pressure and flow rate of breathing gas, that term doesn’t really do it justice- the regulators (a primary and a secondary) are pieces of a more sophisticated system. That system provides us with a main and an alternate source of breathing gas, connects to our information systems so we know some critical things like cylinder pressure, and allows us to effortlessly inflate our BCD.

OK, I lied a little about the physics part, but it’s important to know WHY you need an air delivery system. The human respiratory system is unable to tolerate large differences in pressure, and at depth the ambient (atmospheric plus hydrostatic) pressure is sufficiently high that our lungs cannot expand against that pressure. For this reason, we cannot breathe through a long tube from the surface, and instead must breathe gas that is delivered to our lungs at a pressure very close to ambient- which increases as we go deeper. A scuba regulator, part of the air delivery system, delivers breathing gas to us at pressures very near to ambient (actually a little less than ambient) when we inhale or when we “demand” the gas, and not at other times. Hence, the term demand air delivery system.

That we have a demand system should help clarify why it sometimes feels like we have to pull gas into our lungs when we breathe, and that can occasionally be a little disconcerting. If the breathing gas were delivered at true ambient pressure, our second stage would flow freely, unrestricted, which could quickly deplete our gas supply. So, the “regulator” delivers breathing gas to us at slightly less than ambient pressure and only when we demand that gas.

Zeagle First Stage Flow Digram

A typical air delivery system is comprised of two regulators: the first stage which reduces cylinder pressure (as we know this is often 3000psi in a full cylinder, and this pressure declines as we breathe from the cylinder) to a more manageable intermediate pressure (around 130psi) which stays constant even as the cylinder pressure falls; and, the second stage, which reduces the intermediate pressure further, to that value of just slightly less than ambient, which varies with depth, so we can breathe normally. It is very important that the second stage deliver gas at ambient pressure, neither so great as to exceed our ability to take in the gas, or so low that we are unable to “pull” hard enough to cause the valve to open. With the second stage delivering gas at the correct pressure, based on our depth, breathing effort throughout the entire dive is constant and we do not have to work harder to breathe as depth increases.

If you think about how we calculate ambient pressure based on depth, one thing becomes apparent. There is a depth at which ambient pressure will exceed the intermediate pressure, and the second stage will be unable to deliver any breathing gas. Fortunately, that depth is in excess of 270FSW, well past the 165FSW outer limit of recreational diving.

Again, I want to stress the system aspect here. The regulators are two parts of a total system which includes the hoses connecting the first and second stages, the low pressure hose for inflating our BCD, and the hose (or port) that allows us to connect our cylinder pressure gauge or computer sensor. All elements of the “system” need to work properly, together.

Now that we have an understanding of the physics, it’s time to talk briefly about the types of regulators that go into our air delivery systems. Starting with the first stage, there are two mechanical variants: piston and diaphragm, each of which reacts based on external water pressure. As the names suggest, the piston type has a piston with a rod that opens and closes the main valve on the first stage, while a diaphragm type has a diaphragm that connects to the main valve through a push rod. In either case, when breathing demand causes a pressure drop across the first stage, the main valve opens, keeping the intermediate pressure at the desired value.

From the user standpoint, there is little difference between a piston and diaphragm type first stage, as long as the regulator is good quality and in good repair. From the technical perspective, there are advantages to either design, none of which outweigh the disadvantages of the other! The main criteria is the regulator’s ability to deliver air when needed, and this can be based on your breathing pattern, type of diving, the potential need to support two divers working hard, water temperature, and other factors.

Possibly more important than the mechanical variant -piston or diaphragm- is the matter of the first stage being balanced or unbalanced. Almost without exception, good quality, high performance first stages are of the balanced design, and there’s solid logic underlying that. A balanced design will deliver gas across the first stage at a consistent rate and do so without regard to the pressure in the cylinder. An unbalanced design makes use of cylinder pressure to help “trip” the main valve, so when the cylinder is full, the valve trips easily with little effort, but as the cylinder pressure declines, the effort required to trip the valve can increase considerably. A balanced design will provide consistent performance at any depth and cylinder pressure, making your breathing efforts likewise consistent, and as a result, your dive more comfortable. If you want a detailed explanation, come by the shop and we’ll talk you through it.

Second stages have been manufactured in a variety of mechanical configurations, just as first stages have been. However, for the purposes of this discussion all use the diaphragm system with a “downstream” valve, and are in fact balanced. The advantages of the balanced design are consistent breathing effort and high gas flow when and if needed, no matter the depth.

Zeagle Second Stage Flow Cut-Away

The second stage reduces the intermediate pressure from ~130psi to the ambient pressure we need in order to breathe with minimal effort. When we inhale, we cause the diaphragm to move and in turn, it pushes against a rod that in turn opens the valve, delivering breathing gas at ambient pressure. The diaphragm is located on the front of the second stage regulator, immediately behind the shiny bits with the manufacturer’s logo. The downstream valve design generally requires little effort to “trip” and opens based on the level of demand- heavy breathing will open the valve fully, delivering as much gas as needed, while in less strenuous diving situations, we can “sip” air. Intermediate pressure in fact serves to assist in opening the valve, so they can be easily adjusted to open with very little breathing effort.

There are other variations in second stage regulator designs, some of which can serve to make the regulator more reliable, certain diving situations easier and make servicing the regulator simpler. While the first stage regulator is a comparatively complicated piece of equipment that should be serviced ONLY by trained technicians, with some instruction the second stage can be field serviced. An Equipment Techniques specialty course will give you insight into what field service you can safely undertake.

So, to end where we began, our air delivery systems work, and I hope that you now have some idea of the difference in designs and how they work. No matter what design you have or you choose, there are a few key things to keep in mind:

An air delivery system is a piece of life support equipment and you safety should be the primary factor in your selection.
In life support, price does mean quality, so get the best you can afford, no matter your skill level or experience.
Your air delivery system delivers critical breathing gas, so choose a system that offers high performance and can be readily serviced.
Seek guidance in making your decisions by buying from an experienced, accredited dealer.

At OVI we’re here to help you choose your air delivery system, configure it properly based on your style and preferences, to provide service and maintenance, and to help you be a safe and comfortable diver.

Filed Under: Open Circuit, Scuba Diving Equipment Tagged With: how things work, regulator, Scuba Dive Training, scuba equipment

Care and Feeding of Your Buoyancy Compensator

February 8, 2011 By nigellakey Leave a Comment

Weight Integrated Buoyancy Device

When we think about our dive systems, we lump various pieces of equipment into a number of systems, each of which has a very specific function and purpose during our dives. The air delivery system clearly delivers breathing air to us, so we can survive in the alien environment underwater. Our environmental system keeps us warm, protects us from scrapes, and helps to make us look good! Our dive information system tells us depth, dive time, no-decompression limit, direction, and more. We understand the need to keep these systems in good repair because a failure, while possibly dangerous, is more often a major annoyance and the potential cause of a scrubbed dive or a shortened trip.

We also need to give equal attention to our buoyancy compensator device, or BCD, as it is an integral part of our dive system. First and perhaps most obviously, the BCD functions as a place to attach our breathing gas cylinder. It also is where we place our weights and is a great device from which to hang various pieces of dive equipment. Seems to me that the longer I dive, the more things I feel I need to take with me in the water. Let’s see…2 dive lights…safe-second retainer…SPG/computer retainer…dive tool, frequently 2…a slate…a noise-maker…several carabiners…SMB and a reel…safety sausage…whistle… My BCD just doesn’t seem to have enough pocket space or attachment points lately.

While apparent from its name, perhaps the most important function of the BCD is to give the diver a way to adjust their buoyancy as needed during the dive. From negative buoyancy to stay pinned on the sand, to positive buoyancy on surface at the end of the dive, the BCD gets adjusted numerous times over the course of the dive. Further, we frequently unclip and reclip accessories while diving.

We carry our dive systems around by picking up the BCD with the cylinder and weights in place, tighten and loosen straps, adjust waist bands, clip and unclip, zip and unzip. Basically, that BCD sees more wear and tear than any other piece of equipment in our dive system. So, it only follows that given the expectations of the BCD, and that it is a component in our portable life support systems, it is deserving of care and attention to ensure it works as expected, and lasts as long as we expect. If you look at your dive system, the investment in your BCD is likely equal to that in your air delivery system or your dive computer. The BCD is not a cheap piece of equipment and it is no less important.

Clearly, like the rest of our dive system, the BCD gets wet during a dive, and depending on where you’re diving, post-dive maintenance needs vary somewhat. So, let’s look at what can be done to ensure your BCD functions correctly and lasts a reasonable period of time. To learn more about maintenance and simple repairs, consider taking an Equipment Techniques specialty course.

The BCD carries our breathing gas, so an obvious check would be the cylinder retention straps, their fasteners, buckles and Velcro, plus their attachment points to the body of the BCD. The harness components of the BCD are what holds it to our bodies once we adjust the harness, so those straps and buckles likewise need to be inspected, along with their attachment points to the BCD body. Check the fabric of the straps for fraying and loose threads, and the buckles to ensure they hold the straps in place once adjusted.

Most BCDs have a number of attachment points (D rings typically) and these are where we mount diving accessories. You might have bungee cord, retractable or coil keepers, clips or carabiners which you use to retain accessories. These are things we don’t want to lose when we use them, so having the BCD attachment points in good repair helps to prevent us making continued donations to Neptune. I’m fairly certain he already has enough dive lights, knives and lead. Look at the sewing where the D ring is attached to the BCD body, and if the ring itself is plastic, make sure it’s not cracked or broken.

Power Inflator

Your BCD is inflatable, so it is subject to internal pressure when it’s inflated. The low pressure inflator hose, usually attached to your first stage, needs to be inspected for kinks and cracks, plus the connector must be checked. The connector on the BCD inflator mechanism should be checked for debris or mechanical damage. The corrugated hose from the inflator mechanism to the BCD bladder needs to be checked for damage, and clearly, the inflator mechanism needs to be checked for function, as does the deflator valve. The bladder of the BCD needs to be airtight and not leak when inflated. Frequently, checking the hoses and bladder are performed with an air supply connected to the BCD, but this can also be completed by manually inflating the BCD and checking for any leakage. At this time, the function of the BCD dump valves should also be verified.

The visual inspection of the BCD continues to check seams where valves are sewn into the body, all sewn areas, condition of the outer shell fabric- in general, looking for wear and tear or improper function. A general inspection should be done before and after every dive, and a more thorough inspection done before and after a series of dives.

A good deal of wear and tear on a BCD is due to abrasive particles in the water, and is more a problem when diving in fresh water where the water can be murky from sand and silt. As the BCD flexes from the diver moving, the particles that are embedded in the fabric will over time damage the fabric. So, following a fresh water dive and preferably before it dries, the BCD needs to be rinsed thoroughly with clean, fresh water to remove the particulate. Aside from the sand and silt, fresh water dives will also likely result in the BCD having residual organic materials left in the fabric. If not cleaned, these can decompose, resulting in mold and mildew and damage to the BCD.

Salt water, while typically containing less sand and silt, does have particulate and – oddly enough- contains lots of salt! If the BCD dries after being in salt water the salt crystals can be even more abrasive damaging than sand and silt from fresh water. So, after salt water diving, and again, before it dries, the BCD needs to be rinsed with clean, fresh water. Sea water also contains organics, and again, mold and mildew can result if the BCD is not thoroughly cleaned.

A session in the pool presents a different issue due to the chlorine present, which can serve to bleach the BCD fabric and over time, weaken the material. Chlorine is highly reactive and public pools are typically heavily chlorinated so after a pool session, just as with lake or salt water diving, the BCD needs to be thoroughly rinsed clean.

I personally have found that using wetsuit shampoo works very well to clean the BCD (and of course your wetsuit and other dive system components) and some formulations even remove salt. There are also treatments that are made specifically to remove salt from dive equipment. After washing, using liquid fabric softener in the rinse water can also help to increase the life of your BCD. The fabric softener remains in the material of the BCD and actually serves to coat strands of fiber, keeping the BCD cleaner, reducing the effects of chlorine bleaching and the deposition of salt crystals. Of course, there’s something to be said for that Mountain Fresh fragrance, too!

Now, we’ve talked about the inspection of your BCD, something you can easily do yourself before and after diving, and that covers the exterior. No less important is the interior of the BCD- the bladder that holds the air, used to keep you neutrally, negatively or positively buoyant, as the situation demands.

The BCD bladder is an integral part of the BCD- it is made from coated fabric which is sewn into the BCD body. While in some cases the bladder can be repaired in the event of a small puncture, if the internal coating is damaged, the BCD will not hold air and cannot be repaired. The only solution is to replace the BCD, and as we noted earlier, your BCD was not an insignificant investment.

During any dive, there is a chance that you’ll get some water in the BCD, usually through the deflator valve or possibly the dump valves. On descending we hold the inflator hose high over our heads and release air from the BCD, and this can result in water entering the BCD bladder. Sometimes, a considerable amount of water enters through the deflator valve, which can present the problem of reducing the BCD bladder volume and can impair the BCD’s ability to provide lift. A good reason to hone those descent techniques!

Cleaning the inside of the BCD then is vital to its function and longevity. Basically, maintenance of the interior of the BCD amounts to little more than a good rinse after diving, to remove lake water, salt water or pool water and any organics or solids. The BCD bladder is rinsed by putting clean, fresh water into the BCD, swishing well, and then dumping the water out. The fresh water is usually added through the deflator valve, the BCD manually inflated, swish-swish, then inverting the BCD (inflator hose down) and releasing the air/water from the BCD. Repeat! Some BCDs have a nifty adapter that allows a garden hose to be attached, making flushing the BCD simple.

It is strongly recommended that you use a commercial BCD conditioner when you rinse out the bladder. The conditioner treats the polymer interior of the bladder, keeping it from hardening and cracking. It also serves to neutralize any traces of organic materials, salt and chlorine, again extending the life of your BCD. Once the BCD is cleaned inside and out, it should be partially inflated and allowed to dry naturally, out of direct sunlight, and certainly never put in a dryer.

Now, to talk about drying your BCD, and any piece of dive equipment for that matter. While it’s tempting to hang it outside in the sun to hasten its drying and to make it sunshine fresh, UV radiation from sunlight is quite harmful to your equipment and can dramatically shorten its life while it also will bleach color from your BCD, wetsuit, etc . While we are diving, our equipment is certainly exposed to UV (sunlight), often unavoidably. There’s no reason to accelerate any damage by drying the equipment in direct sunlight. Dry it in the shade, with good air circulation.

Just as it is a requirement to have your air delivery system inspected and adjusted at least once a year, having your BCD similarly serviced, by a qualified technician, should be on your calendar, too. Repairs, if needed, can be completed, and your BCD returned to you in “next to new” condition, and you can continue to dive with confidence.

For any equipment related issues, or for your continuing education needs, call or some by OVI soon. We’re here to help!

Filed Under: Open Circuit, Scuba Diving Equipment Tagged With: BCD, Buoyancy Control Device, Maintenance

Lights – They’re Not Just for The Scuba Diving at Night

January 25, 2011 By nigellakey Leave a Comment

OK, so I struggled with a cute title for this blog, but I hope that the intent is clear: to shed some light (I can’t help it) on why you should carry a dive light -or even two- with you whenever you’re in the water. That’s right, even during the day, a dive light is a good idea.

During night dives, we carry lights (plural) for obvious reasons: it’s dark in the water and we need the light so we can see things that make night dives interesting; plus, we use the lights to allow us to see our buddies and the rest of the dive group in the water. We typically carry two lights during a night dive, a primary and a back-up in case the primary light was to fail.

During a day light dive there’s no real issue with locating your buddy or the rest of the dive group if the visibility is half-way reasonable, so why would you want to carry a dive light during the day? On a lovely sunny day in the Caribbean or the South Pacific there’s plenty of light to see the reef and structures, the fish and other critters, your instruments, your buddy’s hand signals, and enjoy the experience. Even with cloud cover you can still see all of this, right?

Flat Light Casts a Blue Cast to the Reef

Well, let’s look at a given day-light dive and think about what we see and what might not be so obvious to us. When we splash in and start our descent, we can look down and see the top of the reef or the wall, perhaps the sandy bottom where we’ll start our tour around the reef, possibly some marine life, and certainly the rest of our dive group. As we descend, we do notice that the colour gets a little flat but our eyes gradually adjust to the change. As we continue the dive, we notice the corals and marine life, cruise around some, notice a shark or an eel in a crevice, and if we have a good dive guide, and get a chance to see some smaller marine life that he or she has found for us if we are interested in those macro things.

Sea Fan with White Light Added Back

We might be carrying a camera and snap a few shots of these things. After diving our profile we ascend under control, finish our safety stop, and exit the water by climbing back onto the boat. Sounds like a good dive just happened!

Pygmy Seahorse

But, just a minute, did we see everything that we could? During the dive briefing the dive leader told us that we would find a bright pink anemone on a coral mound. During the dive did we notice the great colors in that anemone, on that nudibranch? Do we even know that this species of coral is actually a bright red color or that the fan coral had a pygmy sea horse on it? Did we even notice things of interest prior to the dive leader pointing them out to us? When we look at a guide to the local marine life we see brightly colored fish and corals- why could it be that they seem “different” to us during our dive?

For me, even after 27 years of diving, I still get a thrill out of seeing that same fish for the 1000^th time, or finding a spotted moray, a lobster or a cleaning station, and I like to find things on my own sometimes. After all, diving is a certain amount of exploration and shouldn’t be merely swimming in a line following the dive leader until we’ve used up our gas supply. I dive to see things, whether that’s marine life, features of a reef or a wreck, and just like on land we see things underwater as light that’s reflected from the object and into our eyes. Therefore, I need light in order to see things. OK, so, where am I going with this?

Well, let me illuminate my thoughts. Harken back to your Open Water Diver training and recall that water is considerably more dense than air, and that density results in some effects on us in an underwater environment- not the least of which is an increase in pressure based on depth (No, this is not an essay on Boyle’s Law, but don’t forget the First Rule of Scuba).

Light Absorption from the Scuba Schools International Open Water Manual

Basically, light is energy, water absorbs energy more than air does due to its density, and therefore, water absorbs light more than air absorbs light. If you recall the basic light spectrum of a rainbow (red through violet) and then put that into context with water depth, you most likely will immediately remember that during that dive at depth, the light was flat, and everything had a bluish hue to it. Well, that is due to the light energy being absorbed by the water- first the reds are absorbed within the first few feet of depth, then orange, then yellow and then green. So, at 60’ (18m) during our dive, the “bright” colors of the spectrum have been absorbed by the water, leaving the bluish (blue, indigo and then violet) portion of spectrum only visible to us. I didn’t intend to make this a detailed discussion on physics, wavelength of light and its corresponding energy, so you’ll have to excuse some of the generalizations I’ve made above.

Now, what does this all mean to us? When we dive, we carry with us a life support system. That is to say that we take our “terrestrial environment” with us when we submerge, as being air breathing, we are unable to breathe underwater without a supply of air; and being accustomed to seeing in the less dense atmosphere that is air, we carry our environment in the small air space inside our mask. So, if we want to see things as they really are, why not carry another piece of our terrestrial environment with us? By that, I mean an underwater or dive light.

First, an underwater light is basically “white” which is to say that it is all parts of the spectrum. When we shine that “white” light on an object, the light is reflected back to our eyes allowing us to see it. Now, the same physics apply here, in that the reflected light can be absorbed by the water but if the light is close to the object, and we are in turn close, the light travels a relatively small distance and thus little of it is absorbed. So, what reaches our eyes is practically the full spectrum. This means that what we “see” is the true color of the object, and automagically, when we shine a light on that anemone we actually see that it is a brilliant green color, with the tips being like neon lights. WOW! Likewise, that Blue chromis has an amazing “dapple” of colors.

Now, during that dive, we swam around the reef and noted that there were all kinds of nooks and crannies in the coral, sponges, rocks, shapes and sort-of-colors. If we had a “white” light with us, not only would we have seen the anemone, but we also could have directed that light into a crevice and seen the red and white banded coral shrimp that were at the cleaning station where the spotted moray eel was sitting there with its mouth wide open, being cleaned! Without the light, we would not have been able to see into the reaches of the crevice.

Now, to throw a little more physics on the wall, a “white” light seems simple enough, but many lights do not produce a “white” light, instead producing a light that has a yellow cast to it. An incandescent light (i.e. a bulb light) is likely to produce this yellowish light, while an LED light will produce a truer, whiter light. The whiter the light, the truer the colors will be in the underwater environment.

Last but not least, a light source provides contrast not only in colour but also in texture. It can also provide a more evident depth of field, making distances more obvious. The advantage in contrast can allow you as a diver to see differences in texture, produce shadows, and as a result, find and see some very interesting things, like that pygmy seahorse! You’ll probably now remember that the dive leader carried a light on our dive, and used it to direct our attention to whatever he or she wanted us to see.

So, to wrap this all up, if like me, you dive to see things, then in order to see things, a light is truly indispensible during any dive. An underwater light restores color, provides contrast and even in the day, allows us as divers to look into and under those cracks, ledges, holes and see the things that, after all, we got into the water to see.

Come and see us at the store, and we can get you set up with right underwater light for your next dive trip!

Filed Under: Marine Life, Open Circuit, Rebreathers, Scuba Diving Equipment Tagged With: light, night diving, spectrum

The Importance of Buoyancy Control for Scuba Divers and Photographers

January 10, 2011 By nigellakey Leave a Comment

To be or not to be…Buoyant that is. With all due respect to the Bard, in reality, neither is appropriate- when we dive, adhering to the Third Rule of Scuba, “Maintain Neutral Buoyancy at Depth”, is clearly important and possibly, no more so than when we think about taking photographs underwater.

In our Open Water Diver training we learned the critical Three Rules of Scuba. Continuous breathing is absolutely a requirement for our safety, as is a slow, controlled ascent and a safety stop. So, how does Neutral Buoyancy really figure into this? Aside from issues related to a saw-tooth dive profile, maintaining proper (that is, neutral) buoyancy is important for other reasons.

On a typical open water dive, we drop in and descend to a depth, a feature or some other pre-determined point, and as we recall from the dive briefing, we have a dive profile that we intend to follow, which is to say that we have a maximum depth and time for this specific dive. The depth is important for nitrogen loading in our tissues, as is time at depth, and we figure a profile to ensure that we are diving safely and within recreational limits. So, maintaining the depth as per the plan has some obvious logic.

Aside from adhering to the depth limits we resolved in our dive plan, we also want to think about what we’re going to see on our underwater tour. Again, in the dive briefing there was discussion about what we might expect to see on this dive, so there is a need to be aware of the depth at certain points during the dive, such that we can see the features. Having neutral buoyancy is important here, as if we are drifting up or down, we are less likely to see the feature. Further, if we are struggling with buoyancy, we are much more likely to make contact with the reef or other underwater structure, possibly causing damage to that or injury to ourselves.

Photography is not much different from seeing with our own eyes. The camera, whether digital or optical, records the light reflected from the subject, and captured on the film (or CCD), just as it was captured by our own eyes. The camera allows for a myriad of possible adjustments to compensate for spectrum absorption and in fact, our eyes make the same sort of adjustments, though we are less aware of them at the time. But, when we are looking at an object our eyes need time to sort out the contrast, look for the details of the object, adjust to the lighting, etc. In an underwater environment, our mind is less familiar with the situation and thus slower to resolve the details- seeing that shrimp can be a challenge at first. Experience helps, of course, as the mind becomes trained and better able to process the information.

Nonetheless, even with our own eyes, we need a few seconds to process the information and to actually “see” the object. That demands our ability to focus on the area of interest, differentiate the background from the subject, resolve the textural differences, and finally, see the subject. This requires some stability to our point of view- if the area of interest has shifting features (light, distance, contrast) it will be very difficult for our eyes and mind to process the dynamic data and capture the image. Shifting features certainly can be caused by moving to and fro, as well as up and down. Now, I think you can see where buoyancy has an impact…

Just as our eyes require some time to adjust to the environment, and our mind requires some time to process the information presented to it, a camera will require some time to adjust for the lighting and resolve the focus before the shutter trips. In some systems, this could truly be a few seconds. OK, so now imagine that you are drifting up and down with your breathing…how will you capture that award winning image? Keep in mind, too, that in most underwater photography situations, just as our eyes require time to resolve the light, texture and contrast, a camera needs time to do the same, and usually this only happens once the shutter release is pressed. If the camera moves relative to the subject after the shutter release is pressed the focus and lighting might not be correct. Further, the shutter speed is likely to be quite slow so camera movement will result in a blurred image.

Let’s go back to a few basics here, keeping in mind that photography is not that much separated from seeing with our eyes. Humans are in reality poor multi-taskers, and especially if something has captured our attention. In a driving situation, our attention can be easily diverted by something we see, causing our focus to shift from something important, like which lane we are in. In a diving situation, if we are focused on an object we are likely to stop paying attention to other matters. We know that if we stop to communicate with our buddy underwater, we are going to forget direction, buoyancy or something else. So, when we stop to look at an object we are likely to forget about our buddy, direction, buoyancy, etc. We need to start reducing variables very early, to prevent our dropping onto the reef, or ascending, or losing our buddy. What variable can we easily reduce? Buoyancy!

If we return to the “3 Rs” of scuba, the first thing we want to do is to regain control, so when we stop to look at that object, we are in control of our buoyancy. If we control buoyancy as an autonomic response, our mind can pay attention to the object and, if we are taking a photograph, we can maintain our focus on the object and capture a good or even great image.

Poor buoyancy control presents a number of problems:

Potential unintended contact with and damage to the reef
Potential unintended contact with a wreck or other structure, with risk of injury
Spooking or injuring marine life
Being unable to clearly see the feature
Being unable to capture a good photograph of the feature

Good buoyancy control allows us a number of benefits:

No risk of unintended reef contact and damage
No risk of unintended structure contact or injury
Marine life is at ease and can be readily observed
We can actually see the feature
We can capture an good photograph of the feature

Good buoyancy control means that we are neither rising nor falling in relation to the feature, and that we are standing off the reef or other structure. Further, it means that our eyes and our mind can pay attention to the feature and truly see it. Finally, if our eyes and mind can resolve the feature, we have the time needed to properly compose a photograph, be sure that our camera is set correctly, approach the marine life cautiously, allow the camera to adjust to the specific situation, allow the focus to be set and the shutter to trip.

Good buoyancy control means stability underwater. It promotes good diving posture, better gas management, less exertion and more opportunity to do what we set out to do in the first place- see things in an underwater environment, undisturbed.

Good buoyancy control takes time and practice. Great buoyancy control takes a lot of time and a lot of practice. It’s a combination of breathing control, body positioning, weighting, equipment configuration and concentration. If you want to get some great underwater shots, think about first working on your buoyancy control before you pick up that camera. If you need to work on buoyancy control, consider a Scuba Skills Update, some local diving, or a specialty course. At OVI we are always ready to do help you improve your skills and enhance your diving experience. Let us know how we can help you.

Filed Under: Digital, Photography, Scuba Dive Training, Skills, Underwater, Video Tagged With: buoyancy, diving skills, Training