A Sharkwreck Mystery - Thirty miles off the coast of North Carolina there is a shipwreck on the bottom, 130 feet down. Swarming around the wreck are dozens of Sand Tiger sharks. They look menacing, but they seem to be very docile. What are they all doing there, in one spot? That's what Jonathan wants to find out. Using a variety of filming techniques, Jonathan attempts to discover the secrets of the Sand Tiger shark gatherings at the wrecks, and does the first ever night dive with these sharks...talk about scary! Swimming with Sea Cows - When manatees were first seen by Columbus, he thought they were mermaids...but he had been at sea for a long time! Today these gentle marine mammals are threatened by loss of habitat and collisions with boats. This segment explores the endangered manatees of Florida and their struggle to survive, as well as some of the people who are working to save them. The Shark with the Long Tail - The Thresher shark may very well be the strangest looking shark in the world, with a tail almost as long as its body. This shark is very rare, almost never seen by divers.... until now. Using advanced diving technology, Jonathan visits a remote reef in the Philippines where Thresher sharks show up every morning to be cleaned by small fish.