A crew of mariners, scientists and filmmakers are followed as they cast off on the Sedna IV, an oceanographic schooner, to sail around the world exploring the beauty of nature, how ecosystems work and conservation challenges facing the planet. 1 The Sharks of Cocos Island Highlighting efforts to save the sharks of Cocos from overfishing 2 The Song of the Humpback Scientists attempt to decipher the secrets behind the songs of humpback whales. 3 Sloths A biologist at a research center on Barro Colorado Island in the middle of the Panama Canal introduces the crew of the Sedna IV to the rare pygmy three-toed sloth and explains why this species is threatened. 4 The Cayman Islands Highlighting efforts to save the Grand Cayman blue iguana from extinction. 5 The Last Jaguars Jaguars are studied by scientists on a private reserve in Costa Rica. Also: examining how the conversion of forest into farmland is threatening their population. 6 The Manatees of Belize Highlighting the work of researchers protecting manatees in Belize. 7 The Turtles of Costa Rica A look at the threats posed to sea turtles that nest on the beaches of Costa Rica. Included: the battle between environmentalists and poachers.