Blue Planet returns to reveal untold stories from magical underwater worlds.

A journey into the last great frontier on earth, the deep. New technology reveals spectacular worlds and species. Once considered empty, we now know life thrives in astonishing abundance.

A look at the surprising connections between the world's oceans, from the icy worlds of the poles to unexpected coasts closer to home.

From winter storms to scorching summers, seasonal seas push animals to be resourceful, adaptable and adventurous. Those who can survive these dynamic seas reap rich rewards. 

Beyond the horizon lies the vast open ocean, a world teeming with extraordinary life where giant blue whales, tiny drifting crabs and tenacious turtles thrive against all odds.

In the tropical seas, year-round sunshine has created the perfect conditions for the ocean's richest habitats to flourish, but survival takes remarkable and surprising ingenuity.