What is a BCD and Why is it so Important?


A scuba BCD or buoyancy compensation/control device is a piece of scuba diving equipment that enables the diver to control their buoyancy.  Although it may appear to be a simple inflatable jacket, there’s more to BCDs than meets the eye.  A scuba BCD consists of various parts amongst which the harness is intended to keep the tank attached to the diver’s back, whilst the pockets and straps are meant to hold the gauges and octopus.  The buoyancy compensation device is basically an inflatable vest that allows the diver to secure essential scuba gear.

Lift Capacity

Scuba BCDs vary in terms of type and style, as well as the weight capacity that they can maintain floating.  In order to test this equipment, the inflatable jacket is placed in the water and weights are attached to it until the BCD sinks.  The lift capacity, as it is properly named, is an important factor when selecting a scuba BCD.  Since people are different from one another in terms of body mass, they need to choose the right BCD with adequate lift capacity.  For example, people with a larger amount of muscle mass in comparison with body fat are less buoyant and these people, commonly known as “sinkers”, require vests with a larger lift capacity.

Ok, so BCDs allows divers to keep their scuba gear afloat, but how do they actually control buoyancy?  This can be achieved by inflating or deflating scuba BCDs, and by performing this action, divers can adjust their buoyancy at the required depth.  Divers usually use both a BCD and a weight belt to enable them to float, ascend and descend according to their liking yet expensive BCDs eliminate the necessity of the weight belt by having an integrated weight system.

Types of BCDs

The diversity of these pieces of equipment is so large that divers can choose from numerous models of BCD.  As far as the type is concerned, two BCD designs are most often bought or rented: BCD jackets and wing models.  A BCD jacket is the most popular form of buoyancy control device, and integrates both a harness and an air bladder which can be swept forward under the diver’s arms in order to maintain balance when required.  The wing/harness system is a BCD that permits inflation at the rear, and it is preferred by divers who need to use twin cylinders or who require to have their front area liberated.

Essential Features

Whilst BCDs can have less or more necessary integrated features, some of them are essential for scuba diving and have to be integrated in any buoyant compensation device. Such features include adjustable bands which hold the cylinders on the diver’s back and allow them to change tanks between diving sessions, low pressure inflators/deflators which are needed to conduct the air from the tank through the regulator to the BCD, and overpressure valves, necessary to let the air escape from the BCD in case the unit becomes overinflated.