A Scuba Diving Buoyancy Control Device (BCD) or buoyancy compensator (BC) is a piece of diving equipment worn by divers to provide:
- Life-saving emergency buoyancy both underwater and on the surface
- The ability to adjust and control the overall buoyancy of the diver and the diver's heavy equipment allowing the diver to achieve neutral buoyancy, i.e. remaining at constant depth, or to descend or ascend in a controlled way
