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BBC One is a TV channel that started broadcasting on the 20th April 1964. It replaced BBC Television.

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Factual: Science & Nature: Nature & Environment

Documentary series, presented by David Attenborough, exploring the planet's oceans.

Wildlife documentary series, presented and narrated by David Attenborough, exploring the planet's oceans.

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The BBC West region started on 1st September 1957 as part of the BBC Television Service, before becoming BBC One West.

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The BBC South West region started on 20th April 1961 as part of the BBC Television Service, before becoming BBC One South West.

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The BBC South region started on 5th January 1961 as part of the BBC Television Service, before becoming BBC One South.

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BBC One region covering Derbyshire, Leicestershire and Nottinghamshire.

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The BBC East region started on 1st May 1959 as part of the BBC Television Service, before becoming BBC One East.

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The BBC North East & Cumbria region started in 1959 (tbc) as part of the BBC Television Service, before becoming BBC One North East & Cumbria.

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Formerly part of a wider BBC One South East region that included London and part of the South region. Separated from BBC One London 2001-09-03 following reorganisation of the South East region.

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Simulcast of BBC One Scotland in high definition. From 14/01/2013

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Simulcast of BBC One Northern Ireland in high definition. From 24/10/2012

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Simulcast of network BBC One in high definition. From 03/11/2010

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Until 03/01/2009 BBC Two Wales (analogue) was known simply as BBC Two Wales. BBC Two Wales (digital) was BBC 2W. From 03/01/2009 BBC Two Wales schedules on both analogue and digital became identical

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Simulcast of BBC Two Wales in high definition

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David Attenborough

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Blue Planet II: Series 1: Episode 5: Green Seas

Green Seas

Episode 5

Episode 5: Green Seas

BBC One - Blue Planet II, Series 1, Green Seas

From enchanted forests to undersea prairies, the planet's green seas teem with life.

The wildlife series narrated by David Attenborough explores the planet's green seas. From enchanted forests to undersea prairies, they teem with life.

It's our green seas, not the blue, that bring life to our oceans. Here sunlight powers the growth of enchanted forests of kelp, mangroves and prairies of sea grass. They are the most abundant but fiercely competitive places in the ocean to live.

The most bountiful kelp forests are found off the tip of southern Africa, where two great oceans collide. Almost a hundred different species of shark patrol these waters, driving one resident - the common octopus - to become the ultimate escape artist. To outwit her nemesis, the pyjama shark, she uses ingenious tactics, never filmed before. 

Along the Pacific coast of North America stand, at 60 metres high, the largest and perhaps most diverse kelp forests in the world. In clearings, bright orange male Garibaldi fish guard territories of short turf seaweed. When spiny urchins invade and graze their crops, the Garibaldi desperately pick them off. But urchins can swarm in vast numbers and even attack and fell the kelp forest itself, creating vast 'urchin barrens'. All is not entirely lost, thanks to the return of a ravenous forest resident - sea otters. Back in the late 1800s, sea otters were hunted for their thick pelts to near extinction. And with them gone, urchin numbers rose, destroying many forests. Today, thanks to protection, sea otter numbers are recovering, along with the health of the forest. In a filming first, we reveal great rafts of sea otters now numbering in their hundreds. 

In warmer waters another green sea takes hold. Off Western Australia, vast prairies of seagrass extend to the horizon. Here, grazing green turtles are stalked by tiger sharks. By keeping turtles on the move, tiger sharks prevent the seagrass meadows from being overgrazed. In this way, sharks have become surprising allies in the fight against climate change - as a patch of sea grass is 35 times more efficient at absorbing and storing carbon than the same area of rainforest.

Once a year, one sea meadow in Australia is overrun by an extraordinary invasion. With the first full moon of winter, strange creatures emerge from the deep - spider crabs. The army marches into the shallows and starts to pile one on top of each other, building mounds over a metre high. They then moult. Soft-bodied and weakened, they must avoid the patrolling four-metre-long stingrays.

Further along the coast, the greatest gathering of cuttlefish in the world takes place, as males battle it out for the right to mate. But even among these giant cuttlefish, the largest of their kind, it's not always size that counts. A smaller, sneaky male uses subterfuge, even pretending to be a female, to confuse rivals and get his girl. Even raising your young can be tough in such a competitive place. A weedy seadragon sets out on an epic quest to give his young the very best start in life.

Vast numbers of the ocean's baby fish start their lives in the green seas. The richest nurseries of all are the mangrove forests. Straddling the boundary between land and sea, they provide shelter for the juvenile fish. But in the mangroves of Western Australia lives a deadly assassin - the 40cm-long zebra mantis shrimp. In a surprising story of betrayal, a male shrimp will abandon his mate of possibly 20 years, trading up for a larger female.

And there is one other green sea that supports more life than all the rest combined. Unlike the mangrove forests and prairies of sea grass, its existence in the open seas is only temporary. Microscopic algae flourish into vast blooms, providing a feast for plankton-feeding fish like billions of anchovies. In Monterey Bay, California, the giant shoals draw in thousands of dolphins, sea lions and humpback whales who all race to claim their share of the feast.

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