Buoyancy compensator devices (BCDs)are used to aid the scuba diver to maintain neutral buoyancy. ‘Positive buoyancy’ causes the diver to rise, ‘negative buoyancy’ results in sinking. Thanks to modern materials science and great product design, buoyancy compensators are better than ever. They come in a variety of styles, sizes and materials – not to mention price range – and have a dozen different built-in helpful devices.
Buoyancy compensators come in three basic styles: wings, jackets or vests.
1) Wing buoyancy compensators are thinner, lighter-weight wrap-ons that have bladders to trap air filled usually from the main tank. They are easy to travel with and provide good lift.
2) Full jacket buoyancy compensators allow for larger air pockets, providing substantial lift to heavier divers or those who carry more weight, such as an extra tank or rocks off the bottom.
3) Vests are the traditional design familiar from WWII movies and look like what most would think of as a ‘life vest’. The style is sometimes called a horse collar or adjustable buoyancy life jacket (ABLJ). The traditional life vest style can be bulky and uncomfortable, since the majority of the jacket is in the front. When inflated it can decrease the freedom of head and arm movement and bump up against anything being examined closely. But it has one major advantage: when a diver floats to the surface in the ABLJ he or she will tend to be forced onto the back.
Most contemporary designs move the diver onto his or her face. If you surface normally that’s not usually a problem. It takes little effort to compensate by using fins and balance to remain upright. But, an unconscious diver floating on his or her back is much more likely to survive at the surface. If there’s no one around to immediately lift them out of the water, or force the diver over, being face down can be fatal within minutes.
Like any sports clothing a buoyancy compensator will need to be tested for fit, since every diver’s body is a little bit different. Some are longer, riding closer to the thighs, others shorter and even above the hip. The shorter styles are particularly useful for women, who tend to have shorter backs than men. Also, the shorter vest helps avoid being bruised in the hips by any integrated weights near the base of the buoyancy compensator. Some styles allow the integrated weights to be quick-released in an emergency.
BCDs come in a wide range of sizes, but be sure to allow for the thickness of the wetsuit or drysuit. A man with a 40 inch chest would probably want a jacket at least 42 inches.
Denier count is important. Denier is a measure of the thread thickness used in the weave of the jacket. A higher denier buoyancy compensator (such as 1,200) will resist scrapes and tears better, but a lower count (400) will be more puncture-proof. Low denier jackets are lighter weight and so are easier to pack and carry, but a higher denier jacket will tend to wear longer. Some buoyancy compensators have layers with different counts to get the best of both features.