"We have tried to find the entrance to the great hydrosphere because we feel that the sea age is soon to come."

So Captain Jacques-Yves Cousteau, a French navy gunnery officer, sums up his motives for devoting fifteen years to pioneering undersea explorations, in the course of which he has made more than 5,000 dives. Cousteau's work is an important Jacques-Yves Cousteau 1910– Claus Meyer/Black Starmilestone on the road of man's return to the sea. The era of the "menfish" began when he, along with Philippe Taillez, another naval officer, and Frédéric Dumas, an experienced civilian diver, made successful descents with the first aqualung a decade ago.

Aqualung equipment consists of one to three tanks of compressed air strapped on the diver's back, a face mask, and a mouth piece through which the diver inhales air from his tanks and exhales. He is completely self-contained….

"The...