More people have walked on the moon than have travelled to the very depths of the deep ocean. David Attenborough journeys into the abyss to show us, for the very first time, strange creatures straight out of the film Alien, many of which are new to science. Terrifying fish with massive teeth that eat prey twice their size and weird jellyfish that flash in the darkness. And deep sea sharks never filmed before and submerged mountain ranges and volcanoes far larger than anything on land.

A look at the survival techniques of creatures that endure the harsh conditions of the Arctic and Antarctic. For six months a year, all is dark at the poles and the temperature drops to minus 40 degrees Celsius. Some animals manage to survive the winter, while others are forced to migrate ahead of the advancing ice.

In the Arctic the polar bear is the top predator, catching seals on the ice and forcing seabirds to nest high up on cliffs. In Antartica the flightless penguins have no ground-based predators to deal with but lurking in the water is the constant threat from leopard seals.