Although 70 per cent of our planet is covered by water, the oceans and many of their inhabitants - such as the blue whale - remain an unexplored mystery. This edition travels to the very depths of the seas to reveal a spectacular variety of life - from alien monsters of the deep to pack-hunting killer whales attacking a grey whale calf.

Also features Making Waves, which shows how some of the sequences in the series were captured.

This programme focuses on the predatory skills of some of the most charismatic hunters found on the planet: whales, dolphins, tuna, shark and rapier-nosed billfish. The open ocean is unimaginably immense - itcovers more than 360 million square kilometres of the Earth's surface. Much of this huge expanse of seawater is marine desert with virtually no sign of life. Yet the fastest and most powerful survive, playing a deadly game of hide-and-seek with their prey. This charts how they track down prey in the seemingly featureless seas, following the extraordinary life of yellowfin tuna from a minute egg to a 200 kilogram, voracious predatory giant.