An adventurous look into sunken caves and other sinkholes, including the famous sacrificial well of the Mayans in Yucatan, the underground springs and caverns of Florida (where mastodon bones were discovered in 1955 along with a child's skeleton carbon-dated to 5000 B.C.), and similar subaqueous chasms where the threat of death is seldom distant. Among other stories is the tale of the first U.S. cave dive (1953), made by Jon Lindbergh in California's Bower Cave. Also described are some dives by Jacques Cousteau's team in the Fountain of Vaucluse near Avignon, where a normally placid pool boils fantastically every spring. Cousteau's team found a frighteningly large underwater chamber, but repeatedly experienced near-asphyxiation: their air hoses were sucking down carbon monoxide from the diesel-powered air compressor. The panic and beauty of the first sightings of grandiose limestone caverns, enormous stalactites and weird Coleridgean settings are affecting and neurasthenic readers won't forget the Stygian blackness in thirty feet of mud in the Mayan well where a flashlight can't be seen. Burgess equates the psychology of the experienced, trained cave diver with that of the good mountain climber; he calls it ""the Christopher Columbus syndrome. . . of being the first to soar through subterranean Grand Canyons."" No matter how highly trained, though, you bet your life on each journey down in a hot/cold sweat.