A BCD. (buoyancy compensation device) allows divers to achieve neutral and positive buoyancy; this is achieved by increasing or decreasing the amount of air in the BCD's air bladders. By transferring air from the diver's tank to the BCD, the diver is able to ascend to the surface. Likewise, by dumping air from the BCD, the diver is less buoyant and can descend to the desired depth.
Some divers delay purchasing a BCD because many think they can rent them just as easily as buy them, but save a lot of money. One thing to keep in mind is knowing your dive gear is an enormous safety factor; if you're unfamiliar with the BCD you're wearing, that can make a sticky situation a bad situation. Each BCD's configuration and buoyancy is slightly different. By renting a different BCD each time you dive, you are inhibiting your ability to have the safest dive possible. A dump valve might be located in the front on one BCD and in the lower back on another.
Until the fairly recent past, scuba diving was considered a man's sport and women who dove wore gear that was designed for men, because gear for women didn't exist. Scuba gear manufacturers have paid attention to that fact that more women are diving and have started making scuba gear for both genders.
What are the differences? One main development for female divers is the placement of the chest strap on the BCD. Some manufacturers have altered the location of the strap while other manufacturers have eliminated it completely. Another gender difference in BCDs is the width and shape of the shoulder straps. BCDs made with males in mind tend to offer wider shoulder straps than do the female styles.
By taking gender into consideration, BCDs now offer a better and safer fit for all divers.
The most common style of BCD is the vest or jacket. This style covers the diver's back, and has shoulder straps and buckles in the front. A BCD should fit you like a comfortably–fitting coat; it should allow you to move freely without binding or slipping.
The ideal BCD fit includes:
Some BCDs have back air bladders while other have wrapping air bladders. There isn't a right or wrong to bladder placement; this is one thing
Regardless of which bladder style you prefer, the BCD must offer enough lift that it can safely bring you to the surface while you are wearing all of your dive gear. All scuba BCDs are tested for lift capability; make sure the model you choose fits your body type. The heaviest divers are muscular men who have little body fat (side note: fat floats, making people with more body fat more buoyant). Divers with a little more natural padding will need a BCD with less lift than will a man who is athletic and carrying very little body fat.
A somewhat newer feature added to BCDs is the notion of an integrated weight system. This offers divers the ability to distribute soft weights around their bodies by putting small (usually 1-5 pounds) pouches of lead shot into various pockets in the BCD, rather than wearing weight only around the waist. Weight integrated BCD's allow the diver to reduce the amount of weight worn on the weight belt and increases the diver's safety factor.
Some of the integrated weight in a BCD can be dumped in case of an emergency. This option is much safer than if a person is only wearing a weight belt without an integrated weight system because if a person is only wearing a weight belt, then if the weight belt is dumped, all of the weight is gone. If a person wearing an weight integrated BCD dumps weight, only a portion of the weight is gone; this allows the diver to have a rapid ascent that is still controlled, which greatly reduces health risks, like the bends.
In addition to buoyancy control, BCDs are frequently used to carry the burden of the diver's gear. D-rings are used to clip items, such as flashlights, gauge boots, regulator and octopus keepers, etc., to the diver to keep them close but not in the way. Make sure the BCD you decide on has enough anchoring points to satisfy your gear needs.
A tank lock makes attaching your tank to your BCD an effortless task. It also reduces the risk of your tank slipping once you enter the water.
Dive gear is commonly known for absorbing and trapping smells; keep your BCD smelling fresh by bathing it with a BCD shampoo. Simply rinsing your gear with fresh water will reduce the amount of residue on the surface, but it won't remove odors.
By clipping quick releases, extenders, and hose holders to your gear and hoses and then to your BCD's D-rings, items like your flashlight, camera, and gauge boot are close at hand without being in the way.
Adding a quick disconnect adaptor or hose to your BCD will decrease the time required to attach your BCD to your air supply.
Make sure the dive gear in hand is yours by writing your name on each piece of your gear. This protects you from accidentally picking up another diver's gear, and vice versa.
The last thing you want to do is find out on the beach or dive boat that something is wrong with your gear, and not have a way to fix the problem. By carrying a save-a-dive kit, you can still safely enjoy your dive or snorkeling adventure just like you planned.