The Abyss work vehicle has the indicator stick on the left-hand side of the steering column, and my own private car has it on the right-hand side. As I change between cars, I frequently end up cleaning my windscreen when I go to make a right-hand turn. Similarly, as a diver you do not consistently use the same BCD on each dive you run the risk of making mistake at critical times when your actions need to be automatic. For this reason as a diver you first major purchase should be your BCD.
A diver’s BCD has more functions than any other piece of dive equipment and is the primary piece of equipment that has made diving accessible to the large number of people who dive today. The BCD has four main functions:
- Control Buoyancy underwater. As a diver descends, the air trapped in his gear and his wetsuit/drysuit will begin to compress according to Boyle’s Law. Because of this compression, the diver becomes less and less buoyant the further he descends. Without a BCD, a diver would be negatively buoyant once he reached his desired depth and would struggle to maintain his level in the water. To maintain neutral buoyancy, a diver adds air to his BCD as he descends to avoid sinking too quickly, and releases air from his BCD as he ascends to avoid floating up in an uncontrolled manner.
- Control Buoyancy on the Surface. On the surface by adding air to his BCD a diver can give himself positive buoyancy and hence can relax and does not need to struggle to stay afloat.
- Attach the tank to the Diver. BCDs have an integrated tank band (or cam band) which holds the tank in place on the diver’s back.
- The BCD Provides Attachment Points for Accessories. Most BCDs have pockets and d-rings to hold scuba diving accessories such as knives, back-up masks, lights, reels and dive slates. Divers should make use of these attachment points to ensure that all their gauges, alternate air source regulators, and accessories are clipped off or tucked away so that they can be easily located and do not drag along the bottom.
However, BCDs vary considerably in design and unique features. Some have integrated weights; some have a pull dumps, perhaps one or two bottom dumps, maybe a shoulder dump. Furthermore, some are wrap-around vest style inflation, some back inflation. Some may have an integrated inflator/Regulator and there is a host of power inflator configurations.
Ideally if you can afford it, then you should buy your main dive gear as a package consisting of BCD, regulator, alternate air supply and computer. However, if you cannot afford that option, then the BCD should be the first major piece of equipment any diver purchases. Regulators and dive computers can be rented, but if you wish to get the most out of diving, own your own personal BCD.