Over 70% the planet is covered by the sea, and the Pacific Ocean alone covers half the globe yet we have explored less than 1% of the ocean floor

Producer Alastair Fothergill

The Blue Planet spans the length and breadth of the world's seas. It takes viewers to the water's murkiest depths and shows the array of wildlife that depends on the ocean to live.

Producer Alastair Fothergill explained why making such a series was important.

"Over 70% of the planet is covered by the sea, and the Pacific Ocean alone covers half the globe, yet we have explored less than 1% of the ocean floor.

"The oceans dominate the world's weather systems, and support an enormous variety of life, from the largest whales to the tiniest plankton.

"The Blue Planet is the definitive exploration of the planet's final frontier - from the deep to the shore, from pole to pole."

Unseen behaviour

The series was co-funded by the US TV network the Discovery Channel. It has been sold to several other countries before its broadcast in the UK.

Dolphins were filmed more intimately than ever before

The Blue Planet has outstripped the BBC's record-breaking science project Walking With Dinosaurs in scale and ambition.

The award-winning Dinosaurs cost �6m and went on to be a hit with audiences in Latin America, Canada, Australia, Japan and Germany.

The Blue Planet employed 20 specialist camera teams and went to 200 locations around the world, descending as far as 3,962 metres (13,000ft).

It captures the previously unseen behaviour of many creatures, such as dolphins.

'Inaccessible world'

Among the underwater spectacles featured are 50 species of fish that had never been filmed before.

The albatross: One of thousands of creatures which live from the sea

At least 10 of these were found to be entirely new to science. Fothergill said: "These are very inaccessible areas. That's why no one, until now, has made a natural history film about the deep ocean."

The series opens with a programme looking at blue whales, the largest animal to have lived to date, but also the most elusive.

Also explored are dolphins and the techniques they use to corral sardines along the eastern coast of South Africa.

Killer whales provide dramatic footage

Breeding squid are also shown laying their eggs off California as are turtles in Costa Rica.

The most striking part of the programme will be a sequence in which 15 killer whales become involved in a seven-hour chase of a grey whale and her calf in the sea off California.

Each programme in the series is followed by a 10-minute short called Making Waves, in which cameramen describe their cutting-edge techniques.

The Blue Planet begins on BBC One on Wednesday, 12 September, at 2100 BST.