Equipment
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.
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Frequently Asked Questions
What is the difference between a jacket BCD and a back-inflate BCD?
Jacket BCDs inflate around the torso, providing more surface flotation and a stable upright position. Back-inflate BCDs put all buoyancy behind the diver, which promotes better horizontal trim underwater but can push you face-forward at the surface. Many divers prefer back-inflate for its streamlined underwater profile.
How do I choose the right BCD size?
BCD sizing is based on your body dimensions — most manufacturers provide sizing charts. The BCD should fit snugly when deflated without restricting breathing. Try it on with a wetsuit or drysuit that you will actually dive in, as these add bulk.
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