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DAN Europe: Breathing and Buoyancy Control


DAN Europe: Breathing and Buoyancy Control
DAN Europe: Breathing and Buoyancy Control

Audrey Cudel focuses her attention on breathing and buoyancy control and stresses the importance of a weight check when you first enter the water.

For those of you who watched Jacques Cousteau's adventures featured in the Silent World documentary dating back to 1956, the first generations of underwater explorers ventured deep equipped with three moderate-sized cylinders harnessed to the back, CG45 air regulators the size of an alarm clock, a shatterproof glass mask over the eyes and nose, a weight belt and rubber foot fins. Overall, it was a 25kg apparatus that relied on the most powerful yet sensitive ballasting system – the human lungs. Also, at the end of the last century, some may recall that their first diving lessons were performed using lung control only before integrating a buoyancy control device at a later stage.

Nowadays, breathing properly while diving is often introduced primarily as a safeguard for new divers to avoid a lung over-expansion injury during an uncontrolled ascent. The golden rule is ‘never hold your breath!'

Beyond the concerns over uncontrolled buoyancy, holding one's breath, or skipping breaths, can also lead to a build of CO2 and other hypercapnia issues. On the flip side, breathing continuously might also lead to hyperventilation issues. Therefore, proper ventilation is essential from a physiological perspective to ensure efficient gas exchange in all tissues by using the tidal volume of the lungs during the immersion. The more significant and/or more uncontrolled the tidal volume during the breathing cycle, the less space and chances for inspiratory and expiratory reserve volumes to provide precise buoyancy adjustment.

The awareness of the impact of such adjustments cannot be fully experienced while propelling oneself through the water but instead in static mode. Propulsion can compensate for a lack of buoyancy control. Its effect is similar to throwing a paper plane in the air – it will forcefully glide until it loses speed and crashes. In contrast, a controlled descent or ascent can be initiated solely using the inspiratory and expiratory lung reserve rather than wasting gas fiddling constantly with a wing or drysuit inflator valve.

Building awareness of breathing cycles by taking normal breathes in a slow rhythm and adding minor adjustments when required is the key to fine-tuning buoyancy control. However, the total lung capacity has limitations and is impacted by external factors such as buoyancy and ballast weight distribution.

Buoyancy distribution varies based on one's gas volume management strategy for adding or removing gas from various parts of equipment throughout the dive, specifically the BCD or wing, counter-lungs and/or drysuits. One size does not fit all; in addition to the amount of gas involved, the proper sizing of each piece of equipment relative to the individual's morphology determines their capacity to efficiently distribute the gas volume to where and when it needs to be.

Scuba Diver in Control
Scuba Diver in Control

It's the same as for the lungs. Minimising the required gas volume in the equipment by correct weighting facilitates buoyancy management, ensuring that the right amount of gas flows in and out. It is common among beginners to believe that being overweight will prevent one from shooting to the surface. However, the amount of gas required to compensate for the excess weight can become unmanageable and most likely disturb the diver's typical breathing pattern and the time required to vent gas, causing them to surface too fast.

Some of the ballast weight we carry as divers is an integral part of our configuration, such as the backplate, regulator, and valves and cannot be modified during the dive. However, there are other variables we can act on. Many of us filled our early diving logs conscientiously ticking equipment boxes and writing down how many kilos of weight we were carrying while ignoring other significant components.

The list is long, but each component matters. Planning to dive high or low-pressure steel cylinders? What is the cylinders' weight? What is the weight change between a full and empty aluminium cylinder? Are you diving in freshwater, saltwater or the Red Sea? Weight-wise, what is the impact of removing some undergarment layers after switching to a heated system? The list of possible combinations is endless, so one needs to know how to make a proper assessment when visiting a new environment or after making changes in one's overall configuration. Any change requires a weight check, which is not time-consuming when entering and preparing to exit the water. Once again, buoyancy relies mainly on lung capacity and starts with draining the gas from all equipment parts.

After filling your lungs to approximately 80 percent of their volume, you should float above the surface, float at the surface with your lungs 50 percent full, and start sinking after exhaling down to 20 percent capacity. However, repeating this check before exiting the water with almost empty cylinders (even more with aluminium or low-pressure steel cylinders) is also wise to ensure one can maintain your buoyancy comfortably at a safety or decompression stop when your tanks have minimal gas. Building experience to master static neutral buoyancy and controlled ascent/descent does not require much depth. Practising in the shallows is potentially safer and more challenging as this is where significant pressure changes occur.

The first benefit or value of mastering buoyancy control is safety:

  • Maintaining your target depth is a safeguard against (no) decompression obligations.
  • Managing neutral buoyancy in static or dynamic mode supports the ability of a team to stay together, communicate and react in an emergency.
  • Building environment awareness is a crucial driver to buoyancy and breathing management choices when diving, for instance, close to a reef, when exhaling in overhead environments (percolation generated by exhaled gas swelling to a ceiling can lead eventually to poor visibility), or when anticipating the impact of salinity changes when entering a halocline.

As a virtuous cycle, buoyancy mastery triggers control. Control leads to comfort, comfort to calm, calm to control, focus and gas-saving to maximise the time spent underwater and make the best out of the moment.

As undersea pioneer Jacques Cousteau once explained: “At night I had often had visions of flying by extending my arms as wings. Now I flew without wings. Delivered from gravity and buoyancy, I flew around in space.” Underwater, weightlessness is a skill to be learned before it can become second nature. It's an achievement. For your House of Cards structure to stand firm, you must start by building a solid foundation. Once a diver masters the ability to hold their position in the water column, they can evolve comfortably and safely in a multidimensional space and position themselves where they want and need to be as part of a team and as part of an environment.

You can see more content from Dan Europe from their regular column, or check out the DAN website for more information about medical advice and diver insurance.

About the author

Audrey Cudel is a cave explorer and technical diving instructor specialising in sidemount and cave diving training in Europe and Mexico.

She is also renowned in the industry for her underwater photography portraying deep technical and cave divers. Her work has appeared in magazines such as Wetnotes, Octopus, Plongeur International, Perfect Diver, Times of Malta, and SDI/TDI and DAN (Divers Alert Network) publications.

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