First programme within this trilogy, about prehistoric life. Zoologist Nigel Marven time travels to the Ordovician, Devonian and Triassic. He finds many deadly creatures of the prehistoric oceans including sea scorpions, giant shelled squid and placoderms.

In the second programme of this trilogy, time-travelling zoologist Nigel Marven continues his CGI enhanced journey through the prehistoric marine world. A visit to the Pliocene era provides an encounter with a giant shark called a Megalodon, whilst in the Eocene he is in search of an ancestral whale.

In the final programme in the trilogy about travelling through the CGI enhanced prehistoric marine world, Nigel Marven visits the Jurassic period where the scary Liopleurodon holds sway, and then on to the Cretaceous to see "Hell's Aquarium", full of nasty creatures.