A BCD (Variable Buoyancy Vest) is a device used in scuba diving to control buoyancy. This vest, also called Jacket or BCD (Buoyancy Control Device), allows divers to add or discharge air into an air chamber inside the vest, thus allowing them to maintain a stable position in the water, ascend or descend as needed .

The BCD is essential for the safety and comfort of diving, as it allows divers to adjust their buoyancy in a precise and controlled way.