Avsnitt 1

Nigel travels back in time to the seventh deadliest sea of all time, the Ordovician period (450 million years ago), where he is attacked by sea scorpions and comes face-to-face with a giant orthocone . He then explores the sixth deadliest sea, the Triassic (230 million years ago), where he encounters a pair of Nothosaurus, the bizarre sea reptile Tanystropheus and the giant primitive predatory ichthyosaur Cymbospondylus, which Nigel keeps at bay through using a cattle prod. Nigel then dives in the fifth deadliest sea, the Devonian (360 million years ago) . In the Devonian, Nigel encounters the strange primitive shark Stethacanthus and the placoderm Bothriolepis and he uses a rounded shark cage to protect himself from the giant predatory placoderm Dunkleosteus.