Nigel Marven continues his adventures in the ancient past. Diving into the Jurassic sea, Nigel risks life and limb literally against a pair of Liopleurodon, the massive pliosaur that dominated the Jurassic oceans. Nigel then travels to "Hell's Aquarium", the shallow sea that covered the American mid-west during the Cretaceous era. Here, he comes face to face with the monster mosasaurs, huge carnviourus reptiles with nasty attitudes. Of course, that's only if he survived his close encounter with the giant shark Megalodon.