As meat-eating dinosaurs roamed the Earth, beneath the waves was an environment filled with ferocious predators and massive aquatic oddities. In this three-part program from the creators of "Walking with Dinosaurs," host Nigel Marven goes back in time to explore the prehistoric world's seven deadliest seas, where giant cephalopods, armor-headed fish, long-necked plesiosaurs, titanic sea turtles, and more reside. AKA: "Chased by Sea Monsters," "Sea Monsters." 90 min. total. Widescreen; Soundtrack: English.