Narrator: This is Nigel Marven. He's a zoologist and an expert in tackling dangerous animals. But his latest adventure is really testing his nerve. He's left the safety of the 21st century behind and traveled back to prehistory.
Narrator: His mission - to visit the seven deadliest seas of all time and to come face-to-face with the most terrifying sea creatures that the Earth has ever known.
Narrator: So far, he has experienced three of the deadly seas, and from here on it's only going to get worse. He's about to meet the owner of these jaws, and worse still, the most lethal shark the world has ever seen. But only if he can escape the Devonian seas, and an armoured fish called Dunkleosteus.