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) mouth through the oral inflation valve. They can be broadly classified as having the buoyancy primarily in front, surrounding the torso and behind the diver. This affects the ergonomics and to a lesser degree, the safety of the unit. They can also be broadly classified as having the buoyancy bladder as an integral part of the construction, or as a replaceable component supported inside the structural body. The buoyancy compensator is one of the items of diving equipment most requiring skill and attention during operation, as control is entirely manual, and adjustment is required throughout the dive as weight reduces