Captain Cousteau and the crew of the Alcyone head northward from Cape Horn to investigate Mexico's fabled Sea of Cortez. The youngest and deepest of all the world's ocean gulfs; the seas is risch with marine creatures - birds and sea lions, fish and mammals. The Cousteau team compile the first complete record of the feeding behaviour of the elusive finback whale, the mating of the mama rays and spawning rites of the grunion.