Scuba Diving Buoyancy Control
Techniques For Controlling Buoyancy While Underwater On Scuba
Aug 2, 2008
A unique aspect of the underwater world is the three dimensions. The only other place this can be experienced is in the zero gravity of outer space, or during specialised training for space travel. In fact, astronauts train underwater to gain exposure to this weightlessness and three dimensions.
The Necessity of Buoyancy Control
Mastering buoyancy control can provide more time underwater by conserving air and energy. Good buoyancy control can also reduce stress on a dive.
Photographers and models use buoyancy control to hover beside delicate gorgonian coral or timid clown fish. On a drift dive it is important to stay in the current and above the bottom.
Decompression during the ascent can sometimes require precise buoyancy control.
The Importance of Buoyancy Control
Many students don’t grasp the importance of buoyancy control during their basic training course. With huge fins providing heaps of thrust, a diver can go anywhere: up, down, sideways. What’s all this fuss about buoyancy control?
However, after a diver has developed the skills at moving through the watery world without conscious thought, the diver can truly appreciate the crucial role of buoyancy control.
Three Controls for Three Dimensional Movement
Three basic controls are used to move in the third dimension: the buoyancy compensator; air in the lungs, and the hands and fins.
For example, there are two ways to get into a location to peer under a ledge on a coral reef. Bore straight in with arms, legs and everything else flapping. Or gently ease down like a tiny submarine. The second option is preferred from a diver’s point of view, and for environmental considerations.
Using Breathing to Control Movement
Correct breathing is needed for good buoyancy control. A diver with neutral buoyancy will rise on the inhale and sink on exhale; so a diver must breathe the right amount of air at the right moment. To hover, breathe in as the negative buoyancy from the exhalation takes effect; and out, just before the inhalation changes the buoyancy to positive.
An average male’s lungs contain 5.8 litres of air; a female about 4.6 litres. A male breathes about half a litre on each breath and about seven litres a minute. This gives a wide range of buoyancy with breath control.
However, this breaks the golden rule of diving: “don’t hold breath on scuba”. So these techniques must be used while fully aware of what is happening to prevent problems such as an air embolism.
Buoyancy Control Example
In this example of a coral ledge, a diver should breathe out to get down to the coral, then take in enough air to reach the neutral point and hold. Final adjustments are done with the hands, not fins. It should be possible to settle beside the ledge with no stirred-up sand. Use one or two fingers on a dead patch of coral for final stability. This technique should ensure anything under the ledge will still be there.
When seen enough, breathe in to get upward movement, push off with the hands and rise off the reef. Once clear of the bottom, the normal breathing cycle can start again. Keep the fins still to avoid stirring up the bottom. Fan with the hands until far enough from the sandy bottom to start using the fins.
It is easy to spot a relaxed diver who has mastered this art. They will have hands nonchalantly tucked in their weight-belt like an old time gunslinger or behind their back. Whenever they venture near the bottom they always leave it with little stirred up sand so the next diver also gets the benefit.
