Award-winning film makers Howard and Michele Hall, specialists in the field of underwater documentary making, capture the astonishing and unusual behaviour of creatures deep within the ocean. The series reveals previously unseen activity by some of the ocean’s great predators, including sharks and whales, while also showcasing many lesser known marine creatures. It also features an extraordinary range of subterranean plant life, from the spectacular kelp forests of the north eastern Pacific Ocean to the coral reefs of the Caribbean.

The sea witnesses a constant battle of wits between the hunters and the hunted as different species continue to adapt and refine their survival techniques. Time-lapse photography captures some amazing animal behaviour, from the opalescent squid who rise from the deep when night falls to the mating dance of a school of giant marbled rays.

The series concludes with a fascinating look at the secrets behind filming in an environment that can be dangerously hostile to humans.