Good buoyancy control is the cornerstone of safe and enjoyable diving. Despite this fact, too many divers lack real skill in this vital area. Anecdotes abound of divers who, due to lack of buoyancy control, have a miserable and stressful time underwater.

Diving fatality statistics highlight the role poor buoyancy plays in dive accidents:

1.In a DAN America analysis of over 900 diving fatalities, buoyancy trouble was reported in 31 percent of cases.[1]

2.A DAN Asia-Pacific study of over 350 Australian deaths found that buoyancy problems were highlighted in at least 17 percent of these incidents. As many earlier reports are incomplete, we suspect the actual figure is higher.[2]

To appreciate what is going on, it can be helpful for less experienced divers to refresh the basics of buoyancy control. We encourage you to visit for a summary of “Buoyancy 101” from basic diver training.

Buoyancy control begins with correct weighting. You should generally aim to be neutral while on the surface with all air drained from your BCD. When you exhale, you should begin to sink.

Incorrect weighting is all too common, and it invariably means OVERWEIGHTED. This process usually begins during basic training when new divers should be taught the importance of being correctly weighted, and should be guided through the steps needed to achieve it. But this is often not the case.

Add and dump air slowly to adjust your buoyancy (Photo by Stephen Frink)

It is not uncommon for instructors to overweight their students for pool and shallow ocean classes so they are not floating all over the place during instruction. This overweighting can make it extremely difficult for a panicking diver (student or otherwise) to reach or remain on the surface if required, and has led to fatalities.

In addition, this practice, unless corrected once the skills are covered, potentially turns “trained” divers loose with an inaccurate notion of how much weight they should use for subsequent dives.

BCD inflator-deflator mechanisms are common causes of buoyancy control problems because poorly maintained mechanisms often jam. Poor design, where the inflator and deflator buttons are close together and/or easily confused, have also caused errors and subsequent buoyancy-related accidents. Careful choice of, and familiarity with, such a device will help to minimise problems:

  1. Your BCD is a mechanical device that needs regular inspection, and professional maintenance.
  2. Know your BCD. Know where the inflate/deflate buttons are located, and how much pressure is required to activate them.
  3. Add and dump air slowly. Sudden adjustments equate to dramatic and dangerous changes in your buoyancy.
  4. Practise in a controlled environment if you are not familiar with the BCD, or if you have not dived for a while.
  5. Check your BCD function before every dive, to ensure the mechanism is working smoothly.

[1] Denoble PJ, Caruso JL, Dear G de L, Vann RD. Common causes of open-circuit recreational diving fatalities. Undersea and Hyperbaric Medicine 2008; 35:393–406.

[2] Denoble PJ, Caruso JL, Dear G de L, Vann RD. Common causes of open-circuit recreational diving fatalities. Undersea and Hyperbaric Medicine 2008; 35:393–406.

For the rest of this article (Scuba Diver Issue 7/2015, AA No.84) and other stories, check out our past issues here or download digital copy here.

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