ABSTRACT
Most of us are near neutrally buoyant; it is relatively easy to keep one’s head above water with a gentle kick. Our body is partly composed of bone, a structural material that is 2-3 times the density of water. The negative buoyancy of the bone is not quite offset by the 20%–40% of our body that is low-density fat [1]. It is partly through our air-filled cavities that include the lungs, trachea, and sinuses that we achieve near neutral buoyancy [2]. But it is the additional equipment we carry or wear that leads to problems. To stay warm we wear a buoyant wetsuit composed of neoprene foam, a compressed air tank that gets lighter as the air is used, and a belt filled with lead weights to counter the effects of the suit and tank. As depth increases the neoprene compresses. Close control of buoyancy is maintained through the use of a buoyancy compensation device (BCD); a collapsible safety vest that can receive air from the tank or mouth (Figure 5.1).
