Tahiti, once a South Pacific paradise, has gradually fallen prey to tourism, technology, and most frightening of all, the nuclear weapon. Whilst exploring the famed underwater MacDonald Seamount, the Cousteau divers are startled by a pre-eruption quake which is a live demostration of the forces that created the Tahitian islands. The Cousteau team dive with local fishermen hunting for the precious black pearls. Captain Cousteau investiagtes the rationale behind the underground nuclear tests taking place around the island of Mururoa.