BCD (Buoyancy Compensator) — What It Is and Why It Matters

A BCD (buoyancy compensator device, also called a buoyancy control device) is an inflatable vest or wing worn by scuba divers to control buoyancy at depth and on the surface. By adding air from the tank via a low-pressure inflator hose or orally, the diver can achieve neutral buoyancy at any depth. Venting air through dump valves allows descent or prevents uncontrolled ascent.

BCDs come in three main designs: jacket-style (wraparound inflation for balanced surface buoyancy), back-inflate (bladder behind the diver for streamlined trim), and wing-style (used with backplate and harness systems in technical diving). Most BCDs also integrate the tank attachment, weight system, and D-rings for accessory clips.