Do you dare dive in the deadliest seas of all time? The makers of the dazzling "Walking With Dinosaurs" invite you to swim with monstrously terrifying - and enormously fascinating - creatures from 100 million years ago. Time-travel through marine history with intrepid explorer Nigel Marven as he dives in the late Cretaceous Sea, the most frightening waters in history. Fight a deadly battle with sea scorpions and a giant tentacled orthocone. See if the lethal scissor-like jaws of a giant Dunkleosteus can penetrate the steel bars of your reinforced diving cage. Have a close call with an angry Basilosaurus, and a shuddering encounter with a 50-foot Megalodon shark. Finally, come face to face with the dreaded Mosasaur, king of the late Cretaceous period. See the deep's most mysterious creatures - from the safety of your couch.