This 477 x 480 pixel image depicts a frightened scuba diver heading for the surface. A minor equipment problem or an encounter with a fearsome-looking (but usually harmless) creature may prompt a rapid ascent. And therein may lie the real danger: if the diver holds his or her breath, for example, pressure can rupture the lungs, and gas can escape into the bloodstream. The embolism can then lead to neurological damage (see "The Physiology of Decompression Illness," by R. E. Moon, R. D. Vann and P. B. Bennett, in this issue). Painting by Gregory Manchess.
