The Most Contaminated Dive: Recovering Human Remains
Photo Credit: Riverside Dive Team
It’s a late Thursday evening, the shift operator at the local sewage plant notices something floating in the first settling pond. Upon closer investigation he discovers that it is a hand… A human hand that still has a ring on its finger. He immediately calls the authorities, when the authorities arrive the investigating process proceeds.
Often as public safety divers we face circumstances that may be dangerous and life threatening; either during the dive, or later when we are at home with our families. The first priority as a public safety diver is our safety and well being. After all there is NEVER a time that two dead bodies are better than one. We should always consider our scope of practice and whether it is within our ability to perform the operation we are considering.
Simple questions to ask ourselves: Is this operation beyond my scope of practice and have I been properly trained for this mission? Do I have the proper haz-mat equipment to do the job safely? Should this be a commercial dive operation?
Every public safety diver should have a solid foundation in the basics of Boyles Gas Law. It is imperative to have a good understanding of how Boyles Gas Law relates to decomposition of human tissues at depth. Let’s take a look at how these gas laws can affect our recovery efforts. When it comes to recovering human remains from a liquid environment there are several factors to consider. It has been said that a body that is at a depth of greater than 100ft will not surface on its own accord. Simply put, gases will be at four times the pressure at this depth as they would be at the surface. The total volume of gas at 100ft is 1/4 of the volume it would be at the surface. The likelihood of gas building at this depth is very unlikely. Depths less than 100ft our recovery efforts become a more complex. Decomposition is able to take place at shallower depths as gas production takes effect in the body.With direct relationship to Boyles Gas Law, the body will begin to lift and make its way to the surface due to the decomposition process within the tissues and increased gas production. Besides the contamination hazards that exist we will also need to be concerned with the buoyancy characteristics of tissues after the process of decomposition has occured. The expansion of the body mass due to gas production is now of greater concern and becomes a buoyancy issue that may have direct consequences with our recovery efforts. We must be able to control our ascent to the surface, when recovering a body at depth.
As public safety divers we expose ourselves to environments that are contaminated to varying degrees, whether it be biological, chemical, pesticides, insecticides or other harmful bacterium, the bottom line is this; any body of water must be considered contaminated. We must understand how important it is to protect ourselves against exposure to elements that may be life threatening. The use of the proper protective equipment will significantly lessen the potential risk of exposure. With this in mind, we must protect our mucus membranes as well as our extremities, in order to best accomplish this we should be diving with a full face mask and a dry suit.
I would like to think that most PSD (should we spell out Public Safety Divers here?)dive units are properly trained and understand the importance of using full face masks, with the knowledge and understanding that 90% of our mucus membranes are located on our face. While there are many FFM available on the market today they will all offer some form of contamination protection, some considerations that should be made are as follows. What is the air volume of the mask, and the positive pressures that will allow a greater possibility for water to enter the mask? Both instances may create buoyancy issues and must certainly be considered. Remember that 1 pint of air is equal to 1 pound of buoyancy, given the fact that the head of most adults will weigh between 4 and 6 pounds (dry weight) this doesn’t seem to have much of an effect as you are still negatively buoyant. However, this may become an issue within your attached hood. Air that escaped from the mask may become trapped underneath your hood which may cause you to become positively buoyant. A recommendation to consider is the use of hood vents to manage the escaped air from the mask. These hood vents can be installed easily, but the placement of the hood vents is crucial. Observe the FFM you are diving, you will notice where the spider straps position themselves when tightened. Placing a vent on each side near the back, directly on top of the hood, this placement is the best position to manage the air that may get trapped underneath the hood.
It is the belief of at, Public Safety Dive Services, that you should consider any and every body of water a contaminated body of water, especially if you are in search of a victim. If you are diving a dry suit, you should be trained by a professional ERDI dry suit instructor that completely understands and is familiar with the diving environment and the proper equipment required for every situation.
You will have several factors to consider when diving a dry suit, which depend on the style, the material, the thermals you wear, and the fit of your dry suit. One major factor is buoyancy, air trapped within your dry suit is directly related to buoyancy and may create potential hazards. We should be trained to manage the air within our dry suit to prevent emergency situations. Here are a few considerations: Use a properly fitted dry suit. Use the appropriate thermals that will offer optimal thermal protection for the water temperature you are diving. Know and practice proper donning techniques. Know and use proper burping procedures. Be properly weighted, consider using a weight harness system that allows air to move within the suit. Understand and use proper inlet and exhaust air management skills, this will allow useful and important air management that will help with buoyancy. Practice emergency skills that help protect you from injury.
In short, every public safety diver should have a solid foundation in the basics of Boyles Gas Law. We need to know how to manage our personal air supply at depth. It is imperative to know how Boyles Gas Law relates to decomposition of human tissue at depth, and how it affects our recovery efforts. Public Safety Dive Services offers training that keeps public safety divers as safe as possible.
Public Safety Dive Services
Bo Tibbetts
ERDI Instructor Trainer – 16061
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Silted out in a wreck? How to avoid this by using proper buoyancy and propulsion techniques
Photo Credit Aldo Ferrucci
Imagine you are diving your favorite wreck and you notice an opening you haven’t seen before… The opening is plenty big for you to get in and the room beyond seems large and easy to navigate; so you swim in planning on making a quick tour and coming right back out. Once you’re inside you only swim around for a couple of minutes, but when you turn around to head back out, all you can see is blackness. Your exit to open water and the surface is now hidden somewhere behind a wall of thick silt. Your dive light only penetrates a few inches into the muck, and you can only see your hand in front of your face once it is pressed against the glass of your mask. As the seriousness of the situation sets in, so does panic.
You never thought it could happen to you; the entrance was huge and you only went in a little ways, but now you’re trapped in complete darkness with no idea which way is out. This situation is all too common, and sometimes ends in tragedy. There are many dangers associated with diving into an overhead environment. Creating a slit-out situation where you are unable to find the exit is on the very top of that list. This can be a very hazardous situation, but can be avoided with proper propulsion techniques, buoyancy control, and trim.
Mastering your buoyancy control is your first step. This doesn’t mean your buoyancy is good, it means you have 100% control of your position in the water column. It’s important to work on this with an instructor, and the SDI Advanced Buoyancy Course is a great place to start. You will learn about proper weighting and master fine tuning your buoyancy with breath control, and you will begin to learn about proper body position and trim. This is the foundation that all of your advanced diving skills are built on.
Once your buoyancy control is dialed in, you can really start working on your trim and swimming techniques. The TDI Intro To Tech course is a great way to perfect your trim and start working on advanced non-silting kicks such as: Frog kick, modified flutter kick, back kick, and helicopter turns. It all starts with your trim. If you are not trimmed out properly, it doesn’t matter how you kick, you’re going to create a messy and dangerous situation in an overhead environment. Once you are properly trimmed out and have a handle on the various advanced kicks, you can move forward and start training for the overhead environment.
At the beginning of your TDI Advanced Wreck or Cavern course, your instructor will make sure you have perfected the non-silting kicks before brining you into the overhead environment. This is essential because these kicks create thrust from your fins that can be controlled and directed as you wish, avoiding stirring up the silty bottom and creating a blackout. Throughout your course, these kicks will become second nature and you will find yourself maneuvering in the water with complete control and efficiency. This combined with the proper guideline procedures and gas management techniques you will learn in these courses will help mitigate many of the risks involved with diving in an overhead environment. To find an instructor near you, visit https://www.tdisdi.com/search/?area=tdi.
For more information on TDI courses offered, visit https://www.tdisdi.com/tdi/get-certified/tdi-diver-level-courses/
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Buoyancy and Rebreathers… Rethinking Your Dance with Archimedes
Photo Credit Pete Nawrocky
Achieving “neutral” buoyancy takes a little work and practice but that perfect state when a diver works out how to eliminate the pull of gravity and fly weightlessly through the water is one of the most enjoyable things about diving. And the wonderful thing is, its part of the basic skills learned in the beginning. Really, there is nothing to it… Well, nothing to it after a few tries on open-circuit (OC). Things change and all bets are off when an experienced diver who prides him or herself on their control and finesse in the water column plugs themselves into a rebreather for the first time!
Let’s recap a few things before we look in more detail about the issues that make divers rethink buoyancy control when they switch from OC to a rebreather.
So-called neutral buoyancy is achieved by adjusting the volume of you and your kit so that the whole “unit” displaces a volume of water weighing exactly the same as you and your equipment. If the volume of water you displace weighs less than you and your kit, there’s some weight “left over” and you’ll sink; if it weighs more, there’s buoyancy to spare and you’ll float. Archimedes Principle pure and simple.
Most people float. Our bodies contain a lot of water and are essentially a very similar density to water. Of course some parts are heavier – things like bones, teeth, muscles, and so on – while other parts are lighter – the air in our lungs, sinuses, ears, digestive system for example. Fat is important too. In fact it is the most important factor because usually there is a fair amount of it, it’s lighter than water and it therefore has a great influence on whether we sink or float naturally. Simply put, lean people are sinkers, and the rest of us float with varying degrees of ease. I read somewhere that the average person needs to add one to three kilos (about two to six pounds) of ballast to be neutral in a swimming pool or fresh water.
And as we know, if a fully kitted-out diver perfectly balances their buoyancy in a swimming pool or a fresh water spring, lake or river, they will float in the ocean. They will displace exactly the same volume of water in both situations, but salt water is around three percent heavier than fresh and consequently generates a greater buoyant force. Because of this, we know that we must add extra ballast to help control our buoyancy when we switch from fresh water to salt.
One other factor to consider is that volume of water a diver and kit displaces changes as they change depth due to compression.
A neoprene wetsuit or drysuit (and to a much lesser extent, a compressed neoprene drysuit) compresses as the pressure at depth increases. In effect, the buoyant effect of these things is lessened. The degree of change is relative to the thickness of the neoprene being worn and how much of it there is, but there will be some change and most will occur relatively near the surface.
To compensate for these slight variations, divers add gas to their flotation devices (BCD, Wing, or Floatation Cell). Drysuit divers must also add gas to compensate for increase pressure squeezing the small volume of gas trapped inside their suit. (For the record, all divers must compensate for depth by adding gas to the very small volume of gas trapped in their mask, although this does not have any effect on buoyancy, just comfort.)
The final factor involved with buoyancy control is the gas in a diver’s body. The volume of gas in their ears and sinuses does not change as they dive, but its density does as outside pressure increases with depth; and divers learn how to equalize those regions. If they fail to do so, they will suffer a ‘squeeze’. There is also gas in the stomach and intestines. It too compresses with depth and returns to its original volume when the diver surfaces, but the volume of this gas is usually too small to notice any change in buoyancy.
But this brings us to the gas in a diver’s lungs. This volume is a large enough to make a real difference to buoyancy, and this is the key area of difference between open-circuit and closed-circuit diving and buoyancy control.
When an open-circuit diver achieves a perfect balance between buoyancy and gravity, she will ascend when she breathes in and descend when she breathes out. Also, rather than taking full breaths every time, she can control this effect by taking partial breaths and breathing with her lungs almost empty or with her lungs nearly full.
This simple “trick” and buoyancy fine-tuning is one of the most difficult for newer divers to master without some guidance. New divers are usually a little nervous and tend to swim their whole dive with their lungs more full than normal. This translates into a need to wear more lead to achieve a balance with their buoyant effect. As this diver gains experience and learns to relax, they will “operate” with more normal lung volumes and will be able to drop a few kilos/pounds of ballast.
Experienced divers understand these small subtleties and will adjust their buoyancy by adjusting their breathing. For example, when an experienced diver wants to rise a little during his dive, he will take a deeper breath; or he may breathe out fully to go under an obstruction.
This aspect of finessed buoyancy control is different with a rebreather. A rebreather diver has all the same general “concerns, controls and influences” as her buddy on conventional scuba. However, she also has the gas inside the loop and counterlungs of her rebreather to contend with as well. And that is where things can get confusing for new closed and semi-closed circuit divers regardless of how much open-circuit experience they bring to the table
Just in case you’re one of the couple of dozen divers who has NOT been inundated with information about rebreathers at some point in the past couple of years, here’s a quick primer on their workings.
A rebreather is an underwater life-support system that carries away the exhaled gas breathed out by its user via a mouthpiece, one-way valve and various large-bore hoses (called the loop). Then it removes the carbon-dioxide – a by-product of the diver’s natural metabolism – from that exhaust gas using the compact little chemistry set at the core of the unit (called the scrubber), replaces the tiny amount of oxygen used by the diver to stay awake and active (this quantity, an average of only about one to two litres per minute, is interestingly not influenced by depth), and finally the rebreather serves up clean, re-oxygenated gas back to the diver via more hoses and another one-way valve and the mouthpiece.
The metabolized oxygen can be added to the loop via a computer-controlled valve/solenoid, via a constant flow orifice, via an adjustable-flow orifice, via a simple manual button similar in function to the manual inflate button on a BCD or wing or a combination of all four depending on the make and type of rebreather.
Also part of this system for re-circulating and processing gas are a couple of flexible bags called counterlungs (some types rebreather only have one counterlung, but let’s focus on those with the more conventional pair of counterlungs for now). One counterlung is on the exhalation side of the carbon-dioxide scrubbing chemistry set and is called the exhalation counterlung, while the other is on the opposing side and is called the inhalation lung.
The loop, counterlungs, scrubber, mouthpiece and all the paraphernalia which joins them, is gas and water tight. During normal operation, these flexible bags “flex” as the diver breathes in and out, but the overall effective displacement of the diver and her kit, is unaffected.
So, when a rebreather diver exhales, there are no bubbles because gas is not released into the water but redirected to flow through the various stages and regions of the rebreather. There is essentially no change in the volume of gas being pushed around the apparatus. Since there is no emptying and refilling of the diver’s lungs from an inflexible metal high-pressure cylinder – the walls of which DO NOT flex – there is no change in the buoyant effect of the additional air in the diver’s lungs.
The diver’s lungs are essentially part of the rebreather loop and this maintains a fixed volume of gas buoyancy remains unchanged during normal operation.
Every new rebreather diver spends some time getting used to this concept. They swim towards an object, take a deeper than usual breath expecting to rise gently and bump straight into the object that they were trying to avoid.
In addition to remembering that on a rebreather, depth of breathing does not control buoyancy, there are two related things worth noting.
The first is being correctly weighted and NOT over-weighted. Using conventional scuba, every breath exhaled into the environment makes the diver and her kit slightly less heavy. Quite apart from the buoyant effects of the lungful of gas disappearing as a stream of bubbles on their way to the surface, all gas has some mass. A litre of air weighs a more than a gram and at a depth of 30 metres (around 100 feet) it’s not unusual for a diver to “consume” 50 to 60 litres every minute. Over the course of an hour’s dive, the weight of gas consumed by an open-circuit diver can make a considerable difference to the balance between the forces of buoyancy and gravity. On a technical dive, it is not unusual for a diver to use several kilos worth of gas. Consequently, the ballast they carry has to help compensate for this “Buoyancy Shift.”
Many OC divers, essentially begin their dives over-weighted. A rebreather diver does not have to consider or account for much buoyancy shift and therefore, should begin the dive correctly weighted. This will help with control throughout all phases of the dive.
Secondly, with the potential to have to manage gas volumes in the wing, drysuit and rebreather loop, it’s recommended to maintain just enough gas in the loop for a full breath and no more. This one-breath volume is the simplest to maintain and control. Having more gas than is required for a single breath adds complexity to an already complex management skill.
In simple terms, if a rebreather diver feels the slightest tug of resistance drawing a full breath from the loop, the loop volume is probably optimal!
As with all in-water skills, it helps to understand the principles at play and the factors making each skill necessary. Then once one understands those issues, practice is the key. And on that score, the best way to practice is with a mentor.
For more information on TDI courses offered, visit httpps://www.tdisdi.com/tdi/get-certified/
Contact SDI TDI and ERDI
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The Importance of Buoyancy Skills
Whether you are a brand new certified diver or an experienced diver, you’ve undoubtedly heard the topic of buoyancy discussed. No, it’s not the name of a newly discovered creature off the coast of Indonesia. Nor is it the newest wreck sunk off the coast of Florida. However, it is arguably the most important skill a diver can master.
So why is buoyancy so important and how will it improve your dives? Mastering buoyancy control will in fact offer you many benefits over the course of your dives to come. Whether you are a novice or a long-time experienced diver that could still use a bit of practice, here are the top three reasons why you should develop good buoyancy skills.
The first and most important reason of all is safety. Sure, we were all taught that diving has inherent risks, but we can minimize these risks through safe diving practices. Controlling your buoyancy is a main component to safer diving not just for you, but for the environment and reef as well.
Having a firm grasp on your buoyancy will allow you to stay safely at the depth you planned for. If you lose control and go too deep, you could exceed your no-decompression limits. If that happens, you now have mandatory decompression obligations to deal with. Do you have enough air for that? Does your buddy? The dangers and complications can quickly add up.
Suppose you are in an environment where you do not have to worry about depth. You are diving on a reef and the bottom depth is only 60FT (18M), without proper buoyancy you won’t sink down to the abyss, but you may come crashing down on to the reef. This is not only bad for the coral but can cause you physical injuries as well. Corals can scrape, cut, sting, and cause your new wound site to become infected. Additionally, many types of coral grow very slowly. Breaking off even a tiny piece can be the loss of years of growth.
Being negatively buoyant is not your only concern. Conversely, you also have to consider the implications of being positively buoyant. One of the tenets of safe diving is always making slow and controlled ascents. With awareness and control of the expanding air in your Buoyancy Compensator Device, you can manage a slow, safe ascent by venting air out of your BCD as you ascend. If you lack good buoyancy control along with the ability to vent expanding air as you ascend, you may find yourself in a dangerous situation such as a runaway ascent.
Safety concerns aside, mastering your buoyancy can also improve your overall dive experience. The reason most of us go diving is to see amazing things and enjoy the underwater world. So naturally you try to maximize the amount of time you spend underwater on each dive. If you can dial in your buoyancy quickly and easily, you spend less time fiddling with your inflator. Constantly adding and releasing air from your buoyancy compensator device wastes air from your tank that could extend your dive time. In addition, good buoyancy allows you to relax more; when you are relaxed, your respiration rate is slower and steadier. This is also going to help you conserve the air in your tank and extend your overall dive time.
Finally, developing good buoyancy skills will offer advantages when expanding into other areas of recreational diving. If you’ve ever considered delving into the world of underwater photography, the first piece of advice any photographer will give you is to make sure you’ve mastered your buoyancy. Getting the best possible shot under water can be tricky enough to begin with so it is imperative you precisely control your position in the water.
By now you are probably wondering how to improve your buoyancy skills. Luckily, you have several options available to you that will help you in your efforts. The most logical suggestion is to enroll in an Advanced Buoyancy course at your local SDI dive center. You can learn all you need to know to master buoyancy control under the guidance of a qualified instructor. There is also no substitute for actual practice. So dive as often as you can wherever and whenever you have the opportunity. The more experience you have, the more your skills will improve. The good news is that once you’ve perfected your buoyancy skills, you will have them for as long as you continue diving.
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The Art of Buoyancy – Controlling Your Ascent and Descent
Photo by Harry Averill
In a way, diving can be compared to flying an airplane; the hardest part is taking off and landing. This is true for diving as well; the ascents and descents are often what cause people the most trouble. Once you’re at depth and neutrally buoyant, it’s “easy peasy.” It’s getting to that point and making a nice controlled ascent to your safety stop and the surface that can be a bit tricky…
Making a controlled ascent and descent can add to your overall enjoyment of the dive as well as help prevent barotraumas (pressure related injury). After a controlled descent you arrive at depth already neutral, calm, relaxed, and ready to enjoy the dive. This a vastly different than the over weighted negative free fall many divers make; struggling to equalize and landing on the bottom causing damage to the reef or wreck and ruining the visibility. This is a bad way to start a dive, and it takes time to regain control and enjoy the remaining portion of the dive. Also, this is often the cause of many pressure related injuries to the ears and sinuses because the diver is descending faster than they can equalize those air spaces.
Making a controlled ascent is important for similar reasons. Making a nice controlled ascent to your safety stop, you arrive neutrally buoyant and can hover effortlessly while continuing to enjoy the marine environment around you. You also avoid injury by allowing time for the expanding gas in your air spaces to escape safely. All too often we see divers “float” up and blow right past their safety stop ending up at the surface wondering what the heck happened. We are going to take a look at how to control your ascent and descent by using the art of buoyancy control.
In order to control your descent, you should remain neutrally buoyant. This seems counterintuitive at first. “If I’m neutral, how am I going to go down?” Well, if you are properly weighted you should really only be descending when you exhale all the gas out of your lungs, and you should only be descending a couple of feet at a time. We were all taught in our open water course, that to be properly weighted and an empty BCD you should float at eye level while holding a full breath. When you exhale, you should become slightly negative and descend, when you take another breath, you should become neutral again. As you descend in this controlled manner, you will need to add small amounts of air to your BCD every few feet to counter the compression of your wetsuit/dry-suit and BCD to remain neutral. This allows you to easily stop your descent to equalize, acclimate to a thermo-cline, make contact with your buddy, watch that dolphin swimming by, or avoid landing on the bottom. Now you will arrive at your target depth already neutrally buoyant, air spaces comfortably equalized, and ready to look for that dolphin you spotted on your way down!
Ascending should be pretty much the same process, just in reverse. You should already be neutrally buoyant, so to ascend you should only need to swim lightly towards the surface. Now it’s extremely important to monitor your dive computer’s ascent rate indicator to make sure you are going up at a safe rate and vent the expanding gas out of your BCD so you do not become positively buoyant. If you become positive, you can find yourself on an uncontrolled ascent to the surface. Floating up, the air in your BCD can begin to expand faster than you can dump it, which makes you even more buoyant and you float up faster while the air in your BCD expands even faster. This is a dangerous situation which can result in a barotraumas or even decompression sickness. To avoid this potentially hazardous situation, pause every few feet on your way up to make sure you are not starting to float towards the surface. This way, once you reach your safety stop, you can easily just hold your position hovering weightlessly showing off your excellent buoyancy skills to that dolphin that decided to come back to play.
Your safety stop is an excellent place to make a final weight check. If you are weighted properly, you should have almost NO air in your BCD at the end of the dive and be perfectly neutral. If you are struggling to stay down, you may need another pound or 2, if you have to add air to your BCD to remain neutral, you can probably take a little weight off for the next dive.
Like everything else, practice makes better. Luckily, on every dive, you have to make at least one descent and ascent, so you may as well use this time to practice. We’ve found that using a line or sloping bottom as a visual reference is a great way to get your ascents and descents dialed in, and suggest using them to hone your skills whenever available. Even better than practicing on your own, is having an instructor help you through it with an SDI Advanced Buoyancy course. Find an instructor near you here!
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Tel: 888.778.9073 | 207.729.4201
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Buoyancy Check in 4 Simple Steps
Photo credit Ray Bullion
A diver should be properly weighted for every dive; using only the amount of weight that is required to increase overall comfort in the water allowing them to easily become neutrally buoyant; increasing overall enjoyment while diving.
You might be asking why? Why should a diver be “properly” weighted and neutrally buoyant? An over-weighted diver will typically rationalize the weight they are using by adding air to their Buoyancy Compensator Device (BCD). What most over-weighted divers do not realize is they are exerting additional effort throughout the dive by dragging around the unnecessary amount of weight they are wearing; which in turn increases the diver’s rate of air consumption, shortening the dive, and adding post dive fatigue. An over-weighted diver might find it troubling to stay off the bottom and accidentally damage the bottom contour of the environment they are in whether it’s a beautiful reef, wreck, or even disturb a critters home in the sand. So what does it mean to be “properly” weighted? When properly weighted, the diver should be able to comfortably hover at a safety stop (at the shallow depth of three to six metres or 10 to 20 feet) without popping to the surface, without exerting any effort to stay down, and without struggling to kick to maintain neutral buoyancy at the end of a dive. With the cylinder now near-empty, the diver should need little to no air in the BCD to hover motionless at the safety stop depth.
Now you might be asking, how do I get properly weighted? Simply put, most often proper weighting is determined through a process of trial-and-error experimentation. To start, you should complete a weight check by completing the following steps:
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- Enter the water wearing all gear and an estimated amount of starting weight. This amount can be the weight you think you will need or the estimated number advised by a dive professional.
- With the regulator in your mouth, take and hold a normal to full breath.
- Deflate your BCD – If you are “properly” weighted you should float at eye level and when you exhale you should descend.
Tip: remember to keep your legs still and do not kick! Any kicking motions will move you upward in the water obstructing your ability to determine the true amount of weight required.
- Add or subtract weight as necessary until you float eye level in the water; vertically at the surface.
It’s worthwhile for a diver to complete or repeat the steps above upon surfacing after a dive. The reason why it’s a good idea to complete a weight check after a dive is to make up for the buoyancy shift your cylinder may have during the dive. When a cylinder is full at the start of the dive, it may be heavier versus a near-empty cylinder at the end of a dive.
For example; see the chart below for a commonly used cylinder in salt water (Luxfer AL80)
| Service Pressure | Capacity | Weight | Full | ½ Full | 500 psi | Empty |
| 3000 psi | 77.4 cf | 31.5 lb | -1.7 lb | +1.3 lb | +3.2 lb | +4.2 lb |
The data above shows when a cylinder is full it is 1.7lbs negatively buoyant. When it’s near-empty with 500PSI remaining; it will be positively buoyant by 3.2lbs.
It’s important to conduct a weight check at the end of the dive to compensate for any buoyancy shift your cylinder may take during your dive to avoid becoming positively buoyant towards the end of the dive.
Once the proper amount of weight is determined, the diver should make note of this number and apply it for future dives in the same exposure protection, gear configuration and environment. In the event any of these factors change; like going from fresh water to salt water (increased buoyancy in salt water) weight requirements will change. Finding your proper weight requirements and completing weight checks more often will reduce additional drag in the water, increase your air consumption rate and in turn increase your dive times. More time in the water often leads to more things to see and more fun to be had! Diving properly weighted will also allow you to glide effortlessly through the water and avoid damaging the underwater world.
Take the next step of fine tuning your buoyancy by taking the SDI Advanced Buoyancy course!
Contact SDI TDI and ERDI
If you would like more information, please contact our World Headquarters or your Regional Office.
Tel: 888.778.9073 | 207.729.4201
Email: Worldhq@tdisdi.com
Managing the quick recovery of drifting divers
SDI/TDI Dive Centre Mike and Ball Dive Expeditions are to be congratulated on a recent Case Study by the Queensland Workplace Health & Safety Department on ‘Managing the quick recovery of drifting divers”. Through their innovative and proactive approach to diver safety MBDE have been highlighted by the Regulator as a leader in the Recreational Diving Industry and SDI/TDI are pleased to be able to acknowledge and pass on this praise.
Mike Ball Dive Expeditions (MBDE) has been operating in Queensland since 1969 offering extended diving trips for certificated divers. The dive sites visited are often more than 160 kilometres off the Cairns coastline, in remote locations or involve deep and technical diving.
Due to the type of diving experiences and remote locations offered there is also an increased risk of ‘missing diver’ events caused by drifting. Dive sites suited to experienced divers are often associated with strong currents that may cause divers to drift away from the vessel after surfacing from a dive.
Divers that drift away from the vessel are at risk of drowning, dehydration, hypothermia and marine animal injuries.
MBDE has implemented two innovative dive safety systems to aid in the quick recovery of divers who have drifted away from the vessel to better control the risk of losing a diver:
- Each diver is provided with a Marine Rescue Radio (MRR) with GPS which allows VHF radio communications.
- MBDE has also developed a Lost Diver Buoy (LDB) system.
These systems form part of MBDE’s Safe SCUBA System, a safety management system that emphasises incident prevention through environmental and customer assessment, supervision and monitoring and training and advice.
To read more about the Case Study go to: www.deir.qld.gov.au/workplace/resources/pdfs/mike-ball-case-study.pdf
Find about more about diving with Mike Ball Dive Expeditions see www.mikeball.com
Helpful hints for the Instructor Search
With the recent eNews announcing that now TDI and ERDI instructors are searchable on https://www.tdisdi.com, we wanted to give you some helpful hints that will ensure that you appear on a search.
For instructor members, here is what is required so that the TDI and ERDI search engines will see you:
- A complete address including street, city, province or state, country and zip/postal code.
- Tip #1: Make sure this address is labeled “Physical” in your profile.
- Telephone number.
- Tip #2: Make sure this number is labeled “Work 1”. It can be your mobile or home, but it needs to be labeled “Work 1”.
- Valid email address. You’ll want those who are searching for an instructor to be able to contact you!
- A member must be renewed.
For dive center members, here is what is required so that the SDI TDI and ERDI search engines will see you:
- A complete address including street, city, province or state, country and zip/postal code.
- Tip #1: Make sure this address is labeled “Physical” in your profile.
- Telephone number.
- Tip #2: Make sure this number is labeled “Work 1”. It can be your mobile or home, but it needs to be labeled “Work 1”.
- Valid email address. You’ll want those who are searching for an instructor to be able to contact you!
- Your facility must be renewed
- Your facility will need to be a SDI, TDI or ERDI dive center or higher to appear.
Your dive center is still not showing? Give a call to HQ or your regional office and we will assist with adding your latitude and longitude coordinates for your facility.