More than 70% of the Earth's surface is covered by ocean, yet this biggest natural habitat on the planet remains almost entirely unexplored. This program reveals the mysteries and richness of the unseen seas, from silent, dark depths to the tumultuous, forbidding coasts. This portrait of Earth reveals the splendors of the ocean, its fundamental role in the cycle of life, and also the dangers that threaten it, as well as profiling the people fighting to save it. Discover fresh water in all its amazing forms, including glaciers, waterfalls, deltas and rivers. Travel from the African continent to the American Southwest to see how water is used and why it is so important to preserve this resource.