In this spectacular feature-length documentary, oceanographer Jacques Cousteau and an NFB crew sail up the St. Lawrence River to the Great Lakes on board the specially equipped vessel, the Calypso. They explore the countryside from their helicopter and plumb the depths of the waters in their diving saucer. They encounter shipwrecks, the Manicouagan power dam, Niagara Falls, the locks of the St. Lawrence Seaway and an underwater chase with caribou.

This documentary records the journey undertaken by Jacques Cousteau, his 24-member team, and an NFB film crew to explore the Grand Banks of Newfoundland, one of the world's richest fishing areas. They discover shipwrecks, film icebergs and observe beluga whales, humpback whales and harp seals. The film also includes a fascinating sequence showing Calypso divers freeing a calf whale entrapped in a fishing net.

The story of Captain Cousteau’s chief diver, Bernard Delemotte, and freediving champion Jacques Mayol, who crossed the Atlantic Ocean with two little girls to dive with dolphins and whales.