After leaving the Pliocene, Nigel explores the second deadliest sea, the Jurassic (155 million years ago). There, he meets the giant filter-feeding fish Leedsichthys and predators such as the shark Hybodus and the marine crocodile Metriorhynchus. The apex predator of the Jurassic sea is the giant pliosaur Liopleurodon, which Nigel keeps away through spraying putrescine at them when they approach him. Nigel then travels to "Hell's aquarium", the Cretaceous (75 million years ago). The sheer number of different predators present, including sharks, giant predatory fish Xiphactinus and giant mosasaurs, makes the Cretaceous the deadliest sea of all time. In addition to predators, Nigel also encounters a variety of other Cretaceous animals, such as the aquatic bird Hesperornis, plesiosaur Elasmosaurus, pterosaur Pteranodon and giant sea turtle Archelon.