What is the difference between a BC and a BCD?

Answer 1

It is a matter of word choice. BC stands for bouyancy compensator, while BCD stands for bouyancy compensator device. They are the same thing, just under slightly different names. They are further broken into three catagories: jacket/vest, back flotation, and horse collar. The latter is rarer in modern diving gear (think of Jaqcques Cousteau), but can still be seen on a few divers, especially those that do a lot of skin diving. Hope this helps. BC was first brought into official used by SSI (Scuba Schools International) in their open water course (which was the first course in scuba to be offered to the public ) and then later, PADI changed it to BCD - basically, to be different. Adding onto what was said above, i have never heard of buoyancy compensator device, but instead buoyancy control device. Buoyancy control device, i think, is more sensible as as saying that something compensates your buoyancy doesn't really make sense.