DearDiveBuddy.com

Buoyancy control: Photo: Adam ButlerNeutral buoyancy, being weightless, is theoretical for a breathing diver on an open circuit. We will be slightly positive breathing in, a bit negative breathing out. This is an asset we can use to “micro” regulate our depth, giving us greater control by breathing consciously. A rebreather lacks this possibility because of a counter lung that keeps the total volume in the total system (man and machine) constant.

Although this concept is well known, less is written about the difference between dynamic (swimming) and static (hovering) buoyancy. Maybe you already noticed during a dive while being perfectly neutral buoyant during swimming, things change when you stop all movement. You sink. A wrong reaction is fining downward to keep depth steady, stirring up a sandy bottom and spending unnecessary energy. Inflate your jacket a bit to get “static” neutrally buoyant and keep your fins together making a photo of that big muray on a steep wall motionless, keeping depth control by breathing consciously. Continuing swimming you deflate a bit on departure to gain your previous “dynamic” neutral buoyancy again. The air you spend for this operation is more than compensated for by the spared air of spending less energy.

The difference gets explained by our slightly inclined body angle while we swim. The water pushes more on our chest than on our back while we move forward, resulting in an upward force. If we swim backwards, turning around to check where our buddy is, the water hits the round tank first, so we tend going down, endangering the coral. So take care and compensate for the loss of this “buoyancy” by inflating a bit or changing body-angle while you swim backwards. Try tipping your head back while swimming backwards to see where you go. Pick a reference point to swim to, to be able to go in a straight line. It’s a nice exercise for the more advanced divers. Do it thou above a sandy bottom to not damage the coral.

A modern BCD (buoyancy control device) or jacket has four ways to deflate, but most divers use the classic way by holding the inflator hose high up with their body a bit in upright position. Nice is just pulling the hose. It has a cord inside connected with the dump valve on the shoulder. If you start to deflate this way, after a while you will prefer it, although some models of BCD require a really strong pull. Try yours.

Then we have two quick dump valves on the right side. One on the shoulder and one on the back. At the beginning it takes a bit to find the position of the string. The one on the back can be useful if you get a bit more experienced and want to descend with your head first, also using your fins to go down. In this case your back is the highest point and the only position from with you can deflate. To practise the use of the quick dump valve use this exercise at the end of a dive with quit a bit of air left in your tank after the safety stop on a sandy bottom and no boat traffic on the surface. Put yourself in horizontal position with your bum a bit up to the right, making the dump valve the highest point. Press the inflator button continuously. As you feel you start going up, pull the string of the dump valve. Let air out till you feel you become slightly negative again. While you do all this, keep the inflator button down continuously. Letting air out at regular intervals to maintain more or less neutral buoyancy. A nice exercise for the more advanced diver.

Now print this article and hit the water, to find out that something as basic as buoyancy control can still enhance. Good luck!