Buoyancy "downward" direction. The center of buoyancy of an object is the centroid of the displaced volume of fluid. Archimedes' principle is named after Archimedes of Syracuse, who first discovered this law in 212 B.C. For objects, floating and sunken, and in gases as well as liquids (i.e. a fluid), Archimedes' principle may be stated thus in terms of forces: — with the clarifications that for a sunken object the volume of displaced fluid is the volume of the object, and for a floating object on a liquid, the weight of the displaced liquid is the weight of the object. More
Buoyancy compensator (diving) uses the casing for load bearing purposes and to protect the bladder, which is a replaceable part. The diver needs to be able to establish three states of buoyancy at different stages of a dive: To achieve negative buoyancy, divers who carry or wear buoyant equipment must be weighted to counteract the buoyancy of both the diver and the equipment. When underwater, a diver often needs to be neutrally buoyant so that the diver neither sinks nor rises. A state of neutral buoyancy exists when the weight of water that the diver displaces equals the total weight of the diver.