Costa Brava Scuba Diving

The primary function of the buoyancy compensator (BC, Buoyancy Control Device or BCD) is to allow you to control your buoyancy in the water; it also allows you to easily float at the surface before and after diving.

While diving you need to be able to control your buoyancy throughout the dive. For example, you need to make a controlled descent at the beginning of the dive and a controlled ascent at the end of the dive, both of which will require you to adjust your buoyancy.

You will also want to be neutrally buoyant for most of your dive and you’ll need to make adjustments when you change depth to compensate for the buoyancy changes.

It also allows you to fine-tune your buoyancy at the bottom, so you swim slightly above the sea bed rather than touching it, which disturbs sediment and damages marine life.

Most modern BCDs used in recreational diving are jacket style and also act as the cylinder harness; many also have integrated weight pockets. All BCDs of this design are descended from the Seaquest ADV, which was introduced in 1984 and revolutionised recreational diving overnight. Other manufacturers, including Mares and Scubapro quickly launched similar designs featuring a jacket design, air bladders behind the diver and running under the arms and a cummerbund release system.

They also feature overpressure relief valves to prevent the air bladder rupturing, pockets for equipment such as dive tables, slates or lights, D-rings and a low pressure inflator.

Technical divers often use a different style of “wing” BCD with all the buoyancy located behind the diver, which leaves the front of the diver clear but are not recommended for beginners as they can push you face down at the surface.

One thing to be aware of is the different release mechanisms for BCDs with integrated weights. It is always a good idea to ask your buddy how the release system works before entering the water.