A 2003 BBC documentary trilogy which used CGI graphics to show life as it existed millions of years ago (as far back as 450 million years ago), focusing on the most bizarre, ferocious, or just downright fascinating creatures to ever inhabit the ocean. It was made by Impossible Pictures who were also responsible for creating the legendary series Walking with Dinosaurs.
The series is hosted by the wildlife presenter Nigel Marven who travels to seven ancient seas in a 24 meter long motorboat and scuba dives in each of them, with the computer generated images of the creatures which would once have inhabited those oceans set against the shots of him diving. The original British title of this series is actually Sea Monsters. All three episodes of the series can be watched here on Documentary Vine, use the numbered tabs beneath the video player or the episode list below to navigate them.