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 aid recyclable materials. Older designs used vertically aligned ribs of foam all around the body, but more modern designs typically feature front and rear slabs of foam buoyancy, with the sides left clear to allow unrestricted rotation and arm movement. Most buoyancy aids are one of three basic designs: All buoyancy aids include some form of strap for tightening the buoyancy aid, preventing it from coming off in the water. Many white water designs feature multiple straps on the shoulders and waist to ensure the buoyancy aid can not be swept off in fast water. They may also include pockets for