At night, in a previously unseen event, tiny organisms that light up when disturbed react to their wingbeats, creating an enchanting bioluminescent firework display. In spring thousands of mobula rays gather in Mexico's Sea of Cortez. Here, unlike the tropics, the seas change with the seasons.

Sun heats the sea, creating rain, winds and huge storms that drive up towards higher latitudes. The tropical oceans drive our planet's weather. Fledglings must eventually take to the wing, but danger lurks beneath the waves - metre-long giant trevally fish leap clear out of the water to snatch the birds. In the Seychelles, half a million terns nest on an island. On another reef, a tusk fish demonstrates a surprising level of ingenuity - tool use - as it uses corals as an anvil to break open clams. Starting in the tropical coral reefs - the most diverse ocean habitat - a baby dolphin is taught the secrets of a coral reef, as its family rubs against a particular gorgonian which may have medicinal properties. 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.

In recent years, our knowledge of life beneath the waves has been transformed.

The blue planet the seas of life