A journey into the extraordinary life and legacy of pioneering marine biologist Edie Widder.

Embark on a global odyssey to discover the largest and least explored habitat on earth. New ocean science and technology has allowed us to go further into the unknown than we ever thought possible.

David Attenborough looks into the ocean's depths to discuss the coelacanth, a primeval fish hidden for 400 million years. Its mysterious movements reveal vital clues about life's journey from sea to land, as well as secrets of evolution and survival.