For centuries, the young men of the Dodecanese Islands, a string of islands in the Aegean Sea between Greece and the coast of Asia Minor, earned their living by diving for sponges. They would descend to the bottom of the sea on just a single breath of air, using as a weight and rudder a flat, marble diving stone called a bellstone. They used this ancient technique of "naked diving" until 1863 when the deep-sea diving suit was introduced into the sponge-fishing...