In recent years, our knowledge of life beneath the waves has been transformed. Using cutting-edge technology, One Ocean takes us on a journey from the intense heat of the tropics to our planet's frozen poles to reveal new worlds and extraordinary never-before-seen animal behaviours.

A ground-breaking journey to the Deep, our final frontier and home to real-life aliens, from monstrous sharks to shrimps in glass cages and perhaps the origin of all life on Earth.

Corals build themselves homes of limestone in the warm, clear, shallow seas of the tropics. Their reefs occupy less than one tenth of one per cent of the ocean floor, yet they are home to a quarter of all known marine species. They are complex, infinitely varied structures providing all kinds of homes for their many residents. There is fierce rivalry for space, for food and for a partner, but the reef is also a place full of opportunity.

The big blue is the world's greatest wilderness, far from shore and many kilometres deep. It's a vast marine desert where there is little to eat and nowhere to hide. Yet it's home to some of the biggest and most spectacular creatures on earth. This episode reveals what it takes to survive in this savage and forbidding world.

It's our green seas, not the blue, that bring life to our oceans. Here sunlight powers the growth of enchanted forests of kelp, mangroves and prairies of sea grass. They are the most abundant but fiercely competitive places in the ocean to live. The most bountiful kelp forests are found off the tip of southern Africa, where two great oceans collide.

On the coast, two worlds collide. Coasts are the most dynamic and challenging habitats in the ocean - that brings great rewards but also great danger. The extraordinary animals that live here must find ingenious ways to cope with two very different worlds. This episode is a roller-coaster ride of heart-stopping action and epic drama, peopled with characters from the beautiful to the bizarre.