Neutral buoyancy diver maintains neutral buoyancy by continuous correction, usually by controlled breathing, as neutral buoyancy is an unstable condition for a compressible object in a liquid. The mathematician Archimedes discovered much of how buoyancy works more than 2000 years ago. In his research, Archimedes discovered that an object is buoyed up by a force equal to the weight of the water displaced by the object. In other words, an inflatable boat that displaces 100 pounds (45 kilograms) of water is buoyed up by that same weight of support. An object that floats in the water is known as being "positively" buoyant.
Buoyancy compensator (diving) II flyers and divers. They were developed in the 1960s and have been largely superseded by wing and vest type BCs, primarily because the buoyancy is concentrated in front of the diver when full, and behind the neck when partially filled, producing a tendency to shift the diver's center of buoyancy towards the head with inflation, which adversely affects the diver's trim underwater. The ABLJ's location on the diver's chest and round the neck provides the best buoyancy distribution of the buoyancy compensater designs when it comes to floating a distressed, fatigued or unconscious diver face-up on the surface in