The 35-ton Californian Greys were nicknamed 'Desert Whales' when a 19th-century whaling captain stumbled on their breeding grounds in the desert lagoons of Baja California. After years of slaughter the whales were eventually protected, and now Captain Jacques Cousteau follows some of the remaining 8,000 as they cover the last part of their 5,000-mile migration from their Arctic feeding grounds. In the desert lagoons Cousteau and his team watch the underwater mating of these giants, the care of the mothers for their young, and make a desperate attempt to save the life of a stranded baby whale.