Captain Cousteau and his ship the Calypso visit the Red Sea, the Indian Ocean and the Gulf of Aden in order to study shark behaviour and to test methods of protecting shipwreck and air crash victims from shark attacks. Ichthyologist Dr. Eugenia Clark joins the Calypso crew to study shark behavior and test shark repellents.

The team travels to the coral reefs of the Indian Ocean, an area teeming with animal and plant life, and where numemous complex relationships between different species are played out on a daily basis. Cousteau and his men find a well-ordered universe housing a highly complex community on the coral reef.

The island ot Europa, in the Mozambique Channel between Africa and Madagascar, is the foremost breeding ground of the mysterious sea turtle. The crew's cameras follow the turtles' mating rituals, the females' laboured journey up the beach to lay their eggs, and the fight for survival of the newly-hatched babies. The Calypso crew films the undersea mating dance and subsequent egg-laying of the sea turtle.

The Calypso divers study finback, sperm and killer whales, monitoring their migratory habits by planting small tags in their skin. Captain Cousteau also recounts the romance and legend of the great whales. Cousteau and his crew implant tracking devices into whales off the coasts of Madagascar and California.

Captain Cousteau and the crew of the Calypso adopt a pair of fur seals off the Cape of Good Hope. During an Atlantic crossing the men begin to establish a relationship of trust and friendship with the mammals. Cousteau and his crew take two wild seal pups aboard for study.

The crew sets out on a treasure hunt to the Caribbean in search of the wreck of La Nuestra Senora de la Concepcion, a Spanish ship that sank over 300 years ago carrying more than $2m in silver and gold.

The divers travel inland to Peru's Lake Titicaca, testing experimental techniques for diving at high altitude for the first time. Deep in the lake they discover a unique species of frog whose lungs have atrophied like fish, they die when removed from the water. Cousteau's divers investigate the lake's legend of Inca treasure. The treasure proves to be illusory, but ancient pottery and a unique species of aquatic frog are found.

The Calypso crew follows 35-ton California gray whales on their annual breeding migration. The crew of the Calypso studies the little-known California grey whale, as this once-endangered species embarks on its 5,000-mile annual breeding migration. The team observes the intimate relationships between these creatures, including mating and the feeding of a baby grey.

The crew observes as 20 million squid amass in coastal waters to mate, spawn and die. In the waters off southern California the Calypso happens upon the savage, yet touching, spawning ritual of the sea arrow squids of the Pacific. From their exotic mating dance to the microscopic battle for survival of the newly-hatched young, the entire cycle is captured on film by the crew.

Cousteau and his team study the life and death of the sea elephant, a massive sea mammal which returns each year to the small island of Guadalupe for ritual combat, mating and breeding. Finally, the divers discover the sea elephants' secret graveyard, 25 fathoms below the waves. The crew studies the massive creatures as they mate and nurse on Guadalupe.

The history of underwater exploration is traced from the days of Alexander the Great to the development of the aqualung in 1942, the first bathyscaphe in 1948, the diving saucer in 1959, through to a new fleet of modern deep sea submersibles. A photographic essay traces man's endeavors and advances in undersea exploration.

After more than 140,000 nautical miles travelled aboard the Calypso, and having shot around two million feet of film, Cousteau shares his personal thoughts on the challenges they face filming the infinite phenomena of the water planet. Cousteau presents a behind-the-scenes look at the motivations and challenges driving his crew.

The Cousteau team follows the spawning migration of the red sockeye salmon from the open sea to the Alaskan waters of their birth, up the Salmon River to remote Fraser Lake.

Truk lagoon in the South Pacific, the site of a fierce battle during WWII, is now home to around 50 sunken Japanese vessels. The crew explores the Pacific lagoon to learn how marine life adapts to foreign matter. The divers discover an uncharted sunken freighter, complete with the skeletons of its long-dead crew.

The crew journey to the Galapagos Islands to study the marine iguana, a mysterious dragon-like creature that has reversed the course of evolution and returned to the sea for food and survival.

The strange geological phenomenon of 'blue holes' is investigated by Captain Cousteau and his team, as they discover an undersea 'cathedral' one hundred feet below the surface.

In the North Aleutian Islands, Cousteau and his crew observe the rough courtship and tender mating of the sea otter, before continuing to Monterey where the otter's existence is being threatened by man-made hazards such as pollution and illegal hunting.

The crew travels to the cypress glades of East Florida to film the manatee, a vegetarian creature of the sea whose closest living relative is the elephant. Learning of the plight of 'Sewer Sam', a manatee trapped in the sewers of Miami, the team attempts to help return Sam to the river.

The crew studies the eight-armed octopus's life cycle and ongoing evolutionary process.

The crew isolates a pair of dolphins to study the species' remarkable sonar system.

The crew films the walrus lolling on Arctic ice floes and swimming in the frigid sea.

The crew dives at night to observe the Nautilus -- a living marine fossil.

The crew swims among crocodiles to capture the quick-tempered hippo in action beneath the water.

The Calypso crew records the plaintive, melodious songs of migrating humpback whales.

The crew climbs glaciers, examines whale bones and watches a volcano.