Blue Planet II (2017) s01e08 Episode Script
Oceans of Wonder - Extra
1 The oceans, seemingly limitless, invoke in us a sense of awe and wonder, and also sometimes fear.
They cover 70% of the surface of our planet, and yet they are still the least explored.
Hidden beneath the waves, right beneath my feet, there are creatures beyond our imagination.
With revolutionary technology, we can enter new worlds .
.
and shine a light on behaviours in ways that were impossible just a generation ago.
In this extended special, we celebrate some of the highlights from the series.
We will journey across the globe .
.
from the warm waters of the tropics .
.
to the coldest seas around the poles .
.
and down into the unexplored depths WHOOSHING .
.
to bring us a new understanding of life beneath the waves.
BIRDS SQUAWK This is Blue Planet II.
The surface of the ocean conceals the many creatures that live beneath.
But not all.
Bottlenose dolphins.
They are extremely intelligent.
And with this intelligence comes playfulness.
They surf .
.
and as far as we can tell, they do so for the sheer joy of it.
But to properly appreciate their true character DOLPHINS SING .
.
you have to travel with them into THEIR world.
A pod of bottlenose dolphins is visiting a coral reef in the Red Sea.
For the youngsters, there are things to be learned here.
DOLPHINS SING The adults lead a calf to a particular bush-like coral called a gorgonian.
And here the adults behave rather strangely.
They deliberately rub themselves through the fronds.
Their calf seems reluctant to do so.
By watching his elders, he may be realising that this is something he ought to do.
Gorgonian fronds, in fact, are covered with a mucus that can have anti-inflammatory and anti-microbial properties.
So maybe the adult dolphins are doing this to protect themselves from infection.
The dolphins' intimate knowledge of the reef is spurring us to search for new medicines here, too.
Tropical coral reefs occupy only a tenth of 1% of the ocean floor.
But their shallow warm waters and stable year-round conditions support some of the most crowded and varied communities to be found anywhere in the oceans.
And there are new discoveries to be made on every one of them.
One creature on Australia's Great Barrier Reef is challenging our understanding of fish intelligence.
A tusk fish, and you can see why it gets its name.
He does something few would have believed a fish could do.
Every morning, he travels to the edge of the reef.
He's searching for something special to eat amongst the coral rubble and sand.
Here's one.
A small clam.
But how to crack it open and get to the meat? He takes it all the way back to his special kitchen .
.
a bowl-shaped coral that has a particular bump on the inside that he always uses.
It's not easy if you have no hands.
Oops! There it goes again.
But he's got great determination .
.
and surprising accuracy.
At last.
So here is a fish that uses tools.
Some fish are much cleverer than you might suppose.
The density of the animals on tropical reefs makes competition inevitable and extreme .
.
not only for those that live within the reefs, but for the birds that fly above them.
BIRDS SQUAWK During the dry season, over half a million terns crowd onto this remote atoll in the Indian Ocean.
Their chicks are still in their dark juvenile plumage.
Those just starting to learn to fly use the shallow lagoon that occupies the centre of the atoll as their training ground.
It's difficult for some of them to stay aloft for long.
Giant trevallies! Usually, they are solitary hunters, but about 50 of them have come here from neighbouring reefs, attracted by this abundance of potential prey.
The fledglings stay out of the water if they can.
They even drink on the wing.
If the trevally are to catch one now, they have to up their game.
So there is a fish here that, amazingly, has a brain capable of calculating the air speed, altitude and trajectory of a bird.
The time comes when every fledgling has to take to the air and collect food for itself.
Their parents lead them to the training grounds.
BIRDS SQUAWK If they are to survive, they must learn quickly.
After a month of practising over the lagoon, the youngsters start to leave and take their chances out over the open sea.
The oceans hold 97% of all the water in the world.
As the sun warms their surface, water evaporates.
The vapour rises into the sky until it cools and condenses into towering clouds.
THUNDER CRASHES And they generate huge storms.
The spin of the Earth deflects these storms, north and south, into cooler latitudes.
As they travel across the sea, storm-driven winds create huge swells.
When the swells reach shallower water, they rise into gigantic waves.
In its lifetime, a large storm can release energy that is the equivalent of 10,000 nuclear bombs.
These are the seasonal seas.
And when they warm in spring, they can suddenly explode with life.
Mobula rays have gathered in Mexico's Sea of Cortez in vast numbers.
Why do they leap? Is it to tell others that they're here? No-one knows.
They feed mostly at night, for that is when vast swarms of plankton rise from the depths.
The disturbance in the water stimulates many of the planktonic creatures to luminesce.
Only now do we have the technology to record their faint glow.
The feasting rays swim through them, creating an extraordinary ballet of life and death.
The richness of these waters is based on microscopic plants, phytoplankton, which bloom on such a massive scale, they benefit us all.
They, together with seaweeds and seagrasses, produce as much oxygen as all the forests and grassy plains on land.
In the shallow waters of the seasonal seas lie great undersea forests.
Giant kelp towers 60 metres high.
These enchanted forests are crowded with life.
Creatures jostle for space and food.
In the fiercely competitive kelp forests off Southern Africa, survival can demand great ingenuity.
A common octopus.
She is waiting for prey to pass by.
A crab will do.
The octopus sets off in pursuit .
.
and then lurks with the patience of an ambush hunter.
But the octopus shares the Cape waters with a great concentration of other predators.
Fur seals .
.
and sharks.
They all eat octopus .
.
if they can find one.
And pyjama sharks are experts .
.
at hunting in the undergrowth.
Time to disappear.
But these tough-skinned little sharks are small enough to reach deep into crevices.
But the octopus is far from finished.
She slips her tentacles into the shark's gills.
That prevents the shark from breathing.
So the shark HAS to let go.
When caught out in the open and vulnerable, this octopus does something truly extraordinary .
.
and never recorded before.
She disguises herself .
.
with a protective armour of shells.
She's hiding in plain sight.
The shark can sense its prey.
But the shells confuse it.
In a forest full of hungry mouths, superior wits allow this octopus to stay alive.
In the underwater forests off northern Japan .
.
the residents of this sunken wreck are waiting for the summer temperatures to reach 16 degrees Celsius.
That, for some, is the time for mating.
A kind of giant wrasse called a kobudai.
This is a male .
.
and in female terms, he's particularly handsome.
He's a metre long and weighs 15 kilos .
.
much larger than the diminutive female.
And he is ready to breed.
He attempts to mate with her, and with any of the other dozen or so females that live in his territory .
.
whenever he gets the chance.
But females from around ten years old take little notice of his advances.
This is because, when any large female reaches a critical body size, she can begin a dramatic transformation.
Over just a few months, particular enzymes inside her body cease to work .
.
and male hormones start to circulate.
As time passes, her head expands and her chin gets longer.
A "she" has changed into a "he".
And with this comes a change in temperament.
The old male who ruled all the females here .
.
is challenged to a face-off.
The more bulbous the head, the more it intimidates an opponent.
The territory has a new ruler.
Only the largest females transform themselves in this way.
But the change enables them to have more mates, so they will have many more offspring carrying their genes.
But a new male can't afford to be complacent.
Inside the body of every kobudai female there is a new male-in-waiting.
At the height of summer, there is an explosion in the population of another forest resident.
But this one is out to attack the very forest itself.
Off the Pacific coast of North America, armies of sea urchins cut through the kelp fronds.
Protected by a coat of spines, with their mouths full of razor teeth, they fell the great stalks.
Behind them, they leave a wasteland, known as an urchin barren.
But help is at hand.
Sea otters.
All other kinds of otters spend much of their lives on land, but sea otters rarely leave the water.
At first, a newly born pup is not a very good swimmer, so its mother spends hours grooming its fur to make it buoyant.
But to provide her youngster with milk and keep herself warm, she must eat up to 30% of her body weight every day.
She does that by eating shellfish.
And urchins are among a sea otter's favourite delicacies.
In the past, sea otters were hunted so intensively for their fur that they came close to extinction.
With them gone, many kelp forests were replaced with urchin barrens.
Today, sea otters are protected.
And as their numbers slowly return, many of the kelp forests are recovering, too.
Now, in some remote places, sea otters are so numerous, they assemble in huge rafts .
.
something that hasn't been seen for over a century.
Coasts are the most swiftly changing of all ocean habitats .
.
because of the tides.
Tides are created as the moon's gravity pulls at the sea.
As the moon circles our planet, the seas rise and fall .
.
typically twice a day .
.
creating the most constantly dynamic landscapes on Earth.
Nowhere else do sea-living creatures face such changeable conditions .
.
with the daily risk of drying out and being scorched by the sun.
Where the tide retreats across a rocky shore, it can leave behind a temporary oasis.
A rock pool.
Seemingly, it's a haven of calm.
But not for long.
Turning minutes into seconds reveals unexpected dramas.
In rock pools, grazers, scavengers and filter-feeders must all make the most of the few short hours before the tide returns.
Anemones gulp down anything they can reach .
.
though some meals are harder to digest than others.
LOW RUMBLING These magical worlds soon become battlegrounds.
A deadly predator with five arms and, on the underside, a mouth.
The ochre starfish.
And it's in search of limpets.
For some, there is no escape.
It engulfs them.
But other limpets have a secret defence.
They deploy a slippery shield .
.
which allows them to slide to safety.
And this limpet has its own personal bodyguard.
A scale worm, with a nasty nip! The starfish prefers food that doesn't bite back.
The limpet carries on, its bodyguard tucked safe under its shell.
But there is one creature that limpets have no defence against.
A clingfish.
It has teeth that can lever under the shell.
.
.
.
and twist the limpet off like a bottle top.
The clingfish then swallows it, shell and all.
Rock pool dramas like these last just a few short hours before the tide returns.
Every day, the sea becomes land, and the land becomes sea .
.
bringing new opportunities.
A Sally Lightfoot crab.
One of thousands of shore crabs just waiting for their moment.
Every day, they gather on the rocky shores of Brazil .
.
waiting for the tide to go out .
.
which exposes their feeding grounds .
.
seaweed-covered rocks, 100 metres from the shore.
Getting there is a race against the tide.
They leap from rock to rock.
These crabs seem to be afraid of the water.
And for good reason.
A moray eel.
The chain moray is a specialist crab-hunter.
Its blunt teeth can easily grip and crush a crab's shell.
It's the crab's deadliest enemy.
But the crabs' feeding grounds are still a long way off.
They must press on.
Halfway.
But their enemy has other ideas .
.
crossing the land .
.
to reset the ambush.
To feed, the crabs must keep going.
But nowhere is safe.
An octopus, also a crab-killer.
The crabs make a dash for it.
Made it! Risking life and limb to graze on these seaweed pastures.
But in two hours' time, when the tide starts to turn, they will have to run the gauntlet all over again.
As we leave our coasts and head for the high seas, we enter the big blue.
Covering over half our planet's surface, it's the world's greatest wilderness.
Here, there is nowhere to hide and little to eat.
It's the marine equivalent of a desert.
But there are rare moments when these empty seas are filled with life.
Lanternfish, off the Pacific coast of Costa Rica.
They're scarcely bigger than minnows, but what they lack in size, they make up for in numbers.
They are one of the most numerous fish anywhere.
Normally, they only come to the surface at night, to feed on plankton, but this immense shoal has risen during the day, almost certainly in order to spawn.
For open-ocean hunters, this would be a bonanza.
DOLPHINS SING Spinner dolphins.
They're named after their acrobatic leaps.
They stick together in a super-pod, 5,000 strong.
And now they have located the shoal, using their echo-sounding calls.
But they have to get to it quickly.
They are not the only hunters here.
Yellowfin tuna have also detected the shoal.
And behind them, with their two-metre wingspans, mobula rays.
Now sailfish, one of the fastest fish in the sea, have joined the chase.
The lanternfish may return to the deep at any moment.
But now the dolphins have got here.
DOLPHINS SING They swim beneath the shoal, pinning it to the surface and forcing the lanternfish to pack more closely together.
And now the sea begins to boil.
The tuna charge into the shoal at over 40mph.
The slower-swimming rays arrive at last.
With their immense mouths agape, they scoop up the lanternfish by the hundred.
The shoal has now been largely dispersed, and the sailfish pick off the survivors.
In just 15 minutes, all that's left is a silvery confetti of scales.
But here, such feasts are only too infrequent.
Whilst the dolphins perform great feats of endurance, others are driven to even greater extremes to find food in this ocean desert.
A sleeping giant.
A sperm whale.
This family is resting between bouts of feeding.
Who knows what the owners of the biggest brain in the planet dream about? One has a calf.
It's about two weeks old, but still dependent on its mother's milk.
It's hungry.
It communicates with its mother using a pattern of clicks.
CLICKING But its mother slumbers on.
The calf, covered in suckerfish, of which it can't yet rid itself, has to be patient.
Sleep over and refreshed, the whales move on.
Sperm whales don't wait for their prey to rise to the surface.
They swim down into the depths to find it.
They take a series of heavy breaths .
.
to saturate their blood with oxygen .
.
then down they go.
This entire family dives together in search of squid.
A mother will push her body to the limits of her endurance, and already it's hard for her calf to keep up with her.
CLICKING The calf sticks to its mother as closely as it can CLICKING .
.
touching her frequently .
.
as if for reassurance.
But 300 metres down, it seems the calf can't hold its breath any longer.
In their early years, calves are forced to sit out the hunt.
The adults continue their dive.
The mother changes her calls into a series of louder and more rapid clicks.
CLICKING She's now using sonar to hunt down shoals of squid.
At 800 metres, a burst of clicks.
CLICKING QUICKENS Then silence.
She's made a catch.
A calf can have a long wait at the surface.
A mother returns from the deep after as much as an hour.
She has a stomach full of squid.
Finally, this hungry calf can take some milk.
It's one of the richest produced by any mammal, and the calf guzzles a bath full of it a day.
It may be six years before a calf masters the art of deep diving and is able to find food for itself.
Over half of all animals in the open ocean drift in currents.
Jellyfish cross entire oceans, feeding on whatever happens to tangle with their tentacles.
And when, by lucky chance, they encounter a patch of sea rich in plankton .
.
their numbers explode.
It's such a successful strategy that jellies are one of the most common life forms on the planet.
But among the jellies, and looking somewhat like them, is a rather more complex and sinister creature.
The Portuguese man o' war.
It floats with the help of a gas-filled bladder, topped by a vertical membrane.
With that serving as a sail, it maintains a steady course through the waves.
Long tentacles trail behind it.
Each is armed with many thousands of stinging cells.
A single tentacle could kill a fish or, in rare cases, a human.
A tentacle has caught this one and reels it in.
It's already paralysed.
This voracious man o' war may collect over 100 small fish in a day.
BIRDS SQUAWK Parts of the open ocean are deeper than the highest mountains that rise on the land.
Now we can dive these uncharted depths to discover what secrets lie beneath.
The deep ocean is as challenging to explore as space.
Ready to carry on with the launch.
All clear.
We know more about the surface of Mars than we do about the deepest parts of our seas.
As we descend into the deep, the pressure increases .
.
and the lights from above all but disappears.
INDISTINCT RADIO CHATTER 200 metres down, we enter an alien world .
.
the twilight zone, a sea of eternal gloom.
Survival here means making the most of every last glimmer.
A squid, but this is one that lives only here.
Its right eye looks permanently downwards.
But its left eye is much bigger and trained upwards to detect the silhouettes of prey swimming nearer the surface.
No wonder it's nicknamed "the cockeyed squid".
And even stranger this is barreleye .
.
a fish with a transparent head, filled with jelly, so that it can look up through its skull.
We now know that the twilight zone is a refuge for an incredible 90% of all fish in the ocean.
CRASHING THUD Humboldt squid.
Two metres long and 50 kilos in weight.
Like most squid, they're voracious hunters.
They've found a shoal of lanternfish, hiding 800 metres down, off the coast of South America.
Their tentacles are armed with powerful suckers with which they grab their prey.
And when there are no more lanternfish to be found, they turn on each other.
This squid has caught a smaller one in its tentacles.
To hide its capture from the rest, it releases a smokescreen of black ink.
But then an even bigger one challenges it .
.
and steals its catch.
Below the twilight zone lies a world of perpetual blackness .
.
leading, eventually, to the deep sea floor.
Here, there is a layer of mud, in places a mile thick.
The deep seabed may at first appear lifeless .
.
but it's home to a unique cast of mud-dwellers.
The sea toad.
This fish has been living for so long here that its fins have changed into something more useful.
Feet.
They help it shuffle about on the sea floor.
The flapjack octopus.
It hovers just above the surface of the mud as it delicately sifts through it, searching for worms.
Down here, over time, organic matter slowly decays WHOOSHING .
.
creating a volcano of methane gas.
RUMBLING AND WHOOSHING In the Gulf of Mexico, these eruptions also release a super-salty liquid.
Brine.
Heavier than seawater, it accumulates in great pools on the sea floor.
A lake of concentrated saltwater, 15 metres deep, at the bottom of the sea.
Cut-throat eels, scavengers, come to the shores of the brine lake in search of something edible.
Spending too long in it can send an eel into toxic shock.
Its only hope is to rise above it.
It manages to escape.
Conditions in the deep sea may be hostile .
.
but, astonishingly, there is more life down here than anywhere else on Earth.
As far down as 3½ miles, there are more species of coral in the deep than on the shallow tropical reefs.
The deep may be full of alien-like creatures, but we are more closely connected to it than we ever thought possible .
.
thanks to great ocean currents.
These currents begin in the frozen poles.
Antarctica.
Here, the surface waters are so cold and heavy that they sink .
.
and that creates immense rivers of water that flow into the deep.
This is the start of a giant network of currents .
.
that flow from the poles to the tropics and back again .
.
linking every ocean.
These currents are in fact crucial to the wellbeing of our planet.
They distribute the sun's heat, maintaining a favourable climate for life on Earth.
From creating the weather to producing oxygen, the seas keep our world healthy.
But just as we are discovering how dependent we are on the oceans, there are worrying signs that they are warming at a faster rate than ever before in human history.
And nowhere is this more extreme than in the Arctic.
Here, in the past 30 years, the extent of the ice in summer has been reduced by 40%.
This sudden warming, most likely a consequence of human activity, is having a profound impact on its wildlife.
Walruses are among those that are seriously affected.
LOW GROWLING The sea ice is retreating from much of the walrus's traditional range, so they now have to haul out on dry land.
But a herd of hundreds of quarrelsome mothers, some weighing almost a ton, is not an ideal nursery.
THEY GRUNT AND GROWL Walruses on land stick together for good reason.
Polar bears.
A full-grown male walrus is gigantic - too big for even a polar bear to tackle.
So the bear is looking for a walrus baby.
THEY SNARL The scent of the bear spreads alarm through the colony.
The walruses retreat into the sea.
The bear knows it won't be able to catch them there.
But she too has young ones to feed.
What is a mother to do? WALRUS BARKS A mother walrus still needs to find a place where her young can rest.
A melting iceberg might do.
But she is not the first to find this one.
Suitable places are already taken.
Other mothers don't want to share.
They too need a patch of ice where they can protect their young.
The desperate mother has no choice but to barge her way in.
THEY GROWL AND SNARL So, this time, everyone loses.
Finding the right place on these melting shores gets harder and harder.
Solving these problems together helps create a bond so strong that the mother will stay in contact with her young for the rest of her life.
But who knows now what their future will be? As we understand more about the complexity of the lives of sea creatures, so we begin to appreciate the fragility of their home.
We are at a unique stage in our history.
Never before have we had such an awareness of what we are doing to the planet, and never before have we had the power to do something about that.
Surely we have a responsibility to care for our Blue Planet.
The future of humanity, and indeed all life on Earth, now depends on us.
To find out more about our oceans with this free poster, call .
.
or go to .
.
and follow the links to the Open University.
They cover 70% of the surface of our planet, and yet they are still the least explored.
Hidden beneath the waves, right beneath my feet, there are creatures beyond our imagination.
With revolutionary technology, we can enter new worlds .
.
and shine a light on behaviours in ways that were impossible just a generation ago.
In this extended special, we celebrate some of the highlights from the series.
We will journey across the globe .
.
from the warm waters of the tropics .
.
to the coldest seas around the poles .
.
and down into the unexplored depths WHOOSHING .
.
to bring us a new understanding of life beneath the waves.
BIRDS SQUAWK This is Blue Planet II.
The surface of the ocean conceals the many creatures that live beneath.
But not all.
Bottlenose dolphins.
They are extremely intelligent.
And with this intelligence comes playfulness.
They surf .
.
and as far as we can tell, they do so for the sheer joy of it.
But to properly appreciate their true character DOLPHINS SING .
.
you have to travel with them into THEIR world.
A pod of bottlenose dolphins is visiting a coral reef in the Red Sea.
For the youngsters, there are things to be learned here.
DOLPHINS SING The adults lead a calf to a particular bush-like coral called a gorgonian.
And here the adults behave rather strangely.
They deliberately rub themselves through the fronds.
Their calf seems reluctant to do so.
By watching his elders, he may be realising that this is something he ought to do.
Gorgonian fronds, in fact, are covered with a mucus that can have anti-inflammatory and anti-microbial properties.
So maybe the adult dolphins are doing this to protect themselves from infection.
The dolphins' intimate knowledge of the reef is spurring us to search for new medicines here, too.
Tropical coral reefs occupy only a tenth of 1% of the ocean floor.
But their shallow warm waters and stable year-round conditions support some of the most crowded and varied communities to be found anywhere in the oceans.
And there are new discoveries to be made on every one of them.
One creature on Australia's Great Barrier Reef is challenging our understanding of fish intelligence.
A tusk fish, and you can see why it gets its name.
He does something few would have believed a fish could do.
Every morning, he travels to the edge of the reef.
He's searching for something special to eat amongst the coral rubble and sand.
Here's one.
A small clam.
But how to crack it open and get to the meat? He takes it all the way back to his special kitchen .
.
a bowl-shaped coral that has a particular bump on the inside that he always uses.
It's not easy if you have no hands.
Oops! There it goes again.
But he's got great determination .
.
and surprising accuracy.
At last.
So here is a fish that uses tools.
Some fish are much cleverer than you might suppose.
The density of the animals on tropical reefs makes competition inevitable and extreme .
.
not only for those that live within the reefs, but for the birds that fly above them.
BIRDS SQUAWK During the dry season, over half a million terns crowd onto this remote atoll in the Indian Ocean.
Their chicks are still in their dark juvenile plumage.
Those just starting to learn to fly use the shallow lagoon that occupies the centre of the atoll as their training ground.
It's difficult for some of them to stay aloft for long.
Giant trevallies! Usually, they are solitary hunters, but about 50 of them have come here from neighbouring reefs, attracted by this abundance of potential prey.
The fledglings stay out of the water if they can.
They even drink on the wing.
If the trevally are to catch one now, they have to up their game.
So there is a fish here that, amazingly, has a brain capable of calculating the air speed, altitude and trajectory of a bird.
The time comes when every fledgling has to take to the air and collect food for itself.
Their parents lead them to the training grounds.
BIRDS SQUAWK If they are to survive, they must learn quickly.
After a month of practising over the lagoon, the youngsters start to leave and take their chances out over the open sea.
The oceans hold 97% of all the water in the world.
As the sun warms their surface, water evaporates.
The vapour rises into the sky until it cools and condenses into towering clouds.
THUNDER CRASHES And they generate huge storms.
The spin of the Earth deflects these storms, north and south, into cooler latitudes.
As they travel across the sea, storm-driven winds create huge swells.
When the swells reach shallower water, they rise into gigantic waves.
In its lifetime, a large storm can release energy that is the equivalent of 10,000 nuclear bombs.
These are the seasonal seas.
And when they warm in spring, they can suddenly explode with life.
Mobula rays have gathered in Mexico's Sea of Cortez in vast numbers.
Why do they leap? Is it to tell others that they're here? No-one knows.
They feed mostly at night, for that is when vast swarms of plankton rise from the depths.
The disturbance in the water stimulates many of the planktonic creatures to luminesce.
Only now do we have the technology to record their faint glow.
The feasting rays swim through them, creating an extraordinary ballet of life and death.
The richness of these waters is based on microscopic plants, phytoplankton, which bloom on such a massive scale, they benefit us all.
They, together with seaweeds and seagrasses, produce as much oxygen as all the forests and grassy plains on land.
In the shallow waters of the seasonal seas lie great undersea forests.
Giant kelp towers 60 metres high.
These enchanted forests are crowded with life.
Creatures jostle for space and food.
In the fiercely competitive kelp forests off Southern Africa, survival can demand great ingenuity.
A common octopus.
She is waiting for prey to pass by.
A crab will do.
The octopus sets off in pursuit .
.
and then lurks with the patience of an ambush hunter.
But the octopus shares the Cape waters with a great concentration of other predators.
Fur seals .
.
and sharks.
They all eat octopus .
.
if they can find one.
And pyjama sharks are experts .
.
at hunting in the undergrowth.
Time to disappear.
But these tough-skinned little sharks are small enough to reach deep into crevices.
But the octopus is far from finished.
She slips her tentacles into the shark's gills.
That prevents the shark from breathing.
So the shark HAS to let go.
When caught out in the open and vulnerable, this octopus does something truly extraordinary .
.
and never recorded before.
She disguises herself .
.
with a protective armour of shells.
She's hiding in plain sight.
The shark can sense its prey.
But the shells confuse it.
In a forest full of hungry mouths, superior wits allow this octopus to stay alive.
In the underwater forests off northern Japan .
.
the residents of this sunken wreck are waiting for the summer temperatures to reach 16 degrees Celsius.
That, for some, is the time for mating.
A kind of giant wrasse called a kobudai.
This is a male .
.
and in female terms, he's particularly handsome.
He's a metre long and weighs 15 kilos .
.
much larger than the diminutive female.
And he is ready to breed.
He attempts to mate with her, and with any of the other dozen or so females that live in his territory .
.
whenever he gets the chance.
But females from around ten years old take little notice of his advances.
This is because, when any large female reaches a critical body size, she can begin a dramatic transformation.
Over just a few months, particular enzymes inside her body cease to work .
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and male hormones start to circulate.
As time passes, her head expands and her chin gets longer.
A "she" has changed into a "he".
And with this comes a change in temperament.
The old male who ruled all the females here .
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is challenged to a face-off.
The more bulbous the head, the more it intimidates an opponent.
The territory has a new ruler.
Only the largest females transform themselves in this way.
But the change enables them to have more mates, so they will have many more offspring carrying their genes.
But a new male can't afford to be complacent.
Inside the body of every kobudai female there is a new male-in-waiting.
At the height of summer, there is an explosion in the population of another forest resident.
But this one is out to attack the very forest itself.
Off the Pacific coast of North America, armies of sea urchins cut through the kelp fronds.
Protected by a coat of spines, with their mouths full of razor teeth, they fell the great stalks.
Behind them, they leave a wasteland, known as an urchin barren.
But help is at hand.
Sea otters.
All other kinds of otters spend much of their lives on land, but sea otters rarely leave the water.
At first, a newly born pup is not a very good swimmer, so its mother spends hours grooming its fur to make it buoyant.
But to provide her youngster with milk and keep herself warm, she must eat up to 30% of her body weight every day.
She does that by eating shellfish.
And urchins are among a sea otter's favourite delicacies.
In the past, sea otters were hunted so intensively for their fur that they came close to extinction.
With them gone, many kelp forests were replaced with urchin barrens.
Today, sea otters are protected.
And as their numbers slowly return, many of the kelp forests are recovering, too.
Now, in some remote places, sea otters are so numerous, they assemble in huge rafts .
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something that hasn't been seen for over a century.
Coasts are the most swiftly changing of all ocean habitats .
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because of the tides.
Tides are created as the moon's gravity pulls at the sea.
As the moon circles our planet, the seas rise and fall .
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typically twice a day .
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creating the most constantly dynamic landscapes on Earth.
Nowhere else do sea-living creatures face such changeable conditions .
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with the daily risk of drying out and being scorched by the sun.
Where the tide retreats across a rocky shore, it can leave behind a temporary oasis.
A rock pool.
Seemingly, it's a haven of calm.
But not for long.
Turning minutes into seconds reveals unexpected dramas.
In rock pools, grazers, scavengers and filter-feeders must all make the most of the few short hours before the tide returns.
Anemones gulp down anything they can reach .
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though some meals are harder to digest than others.
LOW RUMBLING These magical worlds soon become battlegrounds.
A deadly predator with five arms and, on the underside, a mouth.
The ochre starfish.
And it's in search of limpets.
For some, there is no escape.
It engulfs them.
But other limpets have a secret defence.
They deploy a slippery shield .
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which allows them to slide to safety.
And this limpet has its own personal bodyguard.
A scale worm, with a nasty nip! The starfish prefers food that doesn't bite back.
The limpet carries on, its bodyguard tucked safe under its shell.
But there is one creature that limpets have no defence against.
A clingfish.
It has teeth that can lever under the shell.
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and twist the limpet off like a bottle top.
The clingfish then swallows it, shell and all.
Rock pool dramas like these last just a few short hours before the tide returns.
Every day, the sea becomes land, and the land becomes sea .
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bringing new opportunities.
A Sally Lightfoot crab.
One of thousands of shore crabs just waiting for their moment.
Every day, they gather on the rocky shores of Brazil .
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waiting for the tide to go out .
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which exposes their feeding grounds .
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seaweed-covered rocks, 100 metres from the shore.
Getting there is a race against the tide.
They leap from rock to rock.
These crabs seem to be afraid of the water.
And for good reason.
A moray eel.
The chain moray is a specialist crab-hunter.
Its blunt teeth can easily grip and crush a crab's shell.
It's the crab's deadliest enemy.
But the crabs' feeding grounds are still a long way off.
They must press on.
Halfway.
But their enemy has other ideas .
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crossing the land .
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to reset the ambush.
To feed, the crabs must keep going.
But nowhere is safe.
An octopus, also a crab-killer.
The crabs make a dash for it.
Made it! Risking life and limb to graze on these seaweed pastures.
But in two hours' time, when the tide starts to turn, they will have to run the gauntlet all over again.
As we leave our coasts and head for the high seas, we enter the big blue.
Covering over half our planet's surface, it's the world's greatest wilderness.
Here, there is nowhere to hide and little to eat.
It's the marine equivalent of a desert.
But there are rare moments when these empty seas are filled with life.
Lanternfish, off the Pacific coast of Costa Rica.
They're scarcely bigger than minnows, but what they lack in size, they make up for in numbers.
They are one of the most numerous fish anywhere.
Normally, they only come to the surface at night, to feed on plankton, but this immense shoal has risen during the day, almost certainly in order to spawn.
For open-ocean hunters, this would be a bonanza.
DOLPHINS SING Spinner dolphins.
They're named after their acrobatic leaps.
They stick together in a super-pod, 5,000 strong.
And now they have located the shoal, using their echo-sounding calls.
But they have to get to it quickly.
They are not the only hunters here.
Yellowfin tuna have also detected the shoal.
And behind them, with their two-metre wingspans, mobula rays.
Now sailfish, one of the fastest fish in the sea, have joined the chase.
The lanternfish may return to the deep at any moment.
But now the dolphins have got here.
DOLPHINS SING They swim beneath the shoal, pinning it to the surface and forcing the lanternfish to pack more closely together.
And now the sea begins to boil.
The tuna charge into the shoal at over 40mph.
The slower-swimming rays arrive at last.
With their immense mouths agape, they scoop up the lanternfish by the hundred.
The shoal has now been largely dispersed, and the sailfish pick off the survivors.
In just 15 minutes, all that's left is a silvery confetti of scales.
But here, such feasts are only too infrequent.
Whilst the dolphins perform great feats of endurance, others are driven to even greater extremes to find food in this ocean desert.
A sleeping giant.
A sperm whale.
This family is resting between bouts of feeding.
Who knows what the owners of the biggest brain in the planet dream about? One has a calf.
It's about two weeks old, but still dependent on its mother's milk.
It's hungry.
It communicates with its mother using a pattern of clicks.
CLICKING But its mother slumbers on.
The calf, covered in suckerfish, of which it can't yet rid itself, has to be patient.
Sleep over and refreshed, the whales move on.
Sperm whales don't wait for their prey to rise to the surface.
They swim down into the depths to find it.
They take a series of heavy breaths .
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to saturate their blood with oxygen .
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then down they go.
This entire family dives together in search of squid.
A mother will push her body to the limits of her endurance, and already it's hard for her calf to keep up with her.
CLICKING The calf sticks to its mother as closely as it can CLICKING .
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touching her frequently .
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as if for reassurance.
But 300 metres down, it seems the calf can't hold its breath any longer.
In their early years, calves are forced to sit out the hunt.
The adults continue their dive.
The mother changes her calls into a series of louder and more rapid clicks.
CLICKING She's now using sonar to hunt down shoals of squid.
At 800 metres, a burst of clicks.
CLICKING QUICKENS Then silence.
She's made a catch.
A calf can have a long wait at the surface.
A mother returns from the deep after as much as an hour.
She has a stomach full of squid.
Finally, this hungry calf can take some milk.
It's one of the richest produced by any mammal, and the calf guzzles a bath full of it a day.
It may be six years before a calf masters the art of deep diving and is able to find food for itself.
Over half of all animals in the open ocean drift in currents.
Jellyfish cross entire oceans, feeding on whatever happens to tangle with their tentacles.
And when, by lucky chance, they encounter a patch of sea rich in plankton .
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their numbers explode.
It's such a successful strategy that jellies are one of the most common life forms on the planet.
But among the jellies, and looking somewhat like them, is a rather more complex and sinister creature.
The Portuguese man o' war.
It floats with the help of a gas-filled bladder, topped by a vertical membrane.
With that serving as a sail, it maintains a steady course through the waves.
Long tentacles trail behind it.
Each is armed with many thousands of stinging cells.
A single tentacle could kill a fish or, in rare cases, a human.
A tentacle has caught this one and reels it in.
It's already paralysed.
This voracious man o' war may collect over 100 small fish in a day.
BIRDS SQUAWK Parts of the open ocean are deeper than the highest mountains that rise on the land.
Now we can dive these uncharted depths to discover what secrets lie beneath.
The deep ocean is as challenging to explore as space.
Ready to carry on with the launch.
All clear.
We know more about the surface of Mars than we do about the deepest parts of our seas.
As we descend into the deep, the pressure increases .
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and the lights from above all but disappears.
INDISTINCT RADIO CHATTER 200 metres down, we enter an alien world .
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the twilight zone, a sea of eternal gloom.
Survival here means making the most of every last glimmer.
A squid, but this is one that lives only here.
Its right eye looks permanently downwards.
But its left eye is much bigger and trained upwards to detect the silhouettes of prey swimming nearer the surface.
No wonder it's nicknamed "the cockeyed squid".
And even stranger this is barreleye .
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a fish with a transparent head, filled with jelly, so that it can look up through its skull.
We now know that the twilight zone is a refuge for an incredible 90% of all fish in the ocean.
CRASHING THUD Humboldt squid.
Two metres long and 50 kilos in weight.
Like most squid, they're voracious hunters.
They've found a shoal of lanternfish, hiding 800 metres down, off the coast of South America.
Their tentacles are armed with powerful suckers with which they grab their prey.
And when there are no more lanternfish to be found, they turn on each other.
This squid has caught a smaller one in its tentacles.
To hide its capture from the rest, it releases a smokescreen of black ink.
But then an even bigger one challenges it .
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and steals its catch.
Below the twilight zone lies a world of perpetual blackness .
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leading, eventually, to the deep sea floor.
Here, there is a layer of mud, in places a mile thick.
The deep seabed may at first appear lifeless .
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but it's home to a unique cast of mud-dwellers.
The sea toad.
This fish has been living for so long here that its fins have changed into something more useful.
Feet.
They help it shuffle about on the sea floor.
The flapjack octopus.
It hovers just above the surface of the mud as it delicately sifts through it, searching for worms.
Down here, over time, organic matter slowly decays WHOOSHING .
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creating a volcano of methane gas.
RUMBLING AND WHOOSHING In the Gulf of Mexico, these eruptions also release a super-salty liquid.
Brine.
Heavier than seawater, it accumulates in great pools on the sea floor.
A lake of concentrated saltwater, 15 metres deep, at the bottom of the sea.
Cut-throat eels, scavengers, come to the shores of the brine lake in search of something edible.
Spending too long in it can send an eel into toxic shock.
Its only hope is to rise above it.
It manages to escape.
Conditions in the deep sea may be hostile .
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but, astonishingly, there is more life down here than anywhere else on Earth.
As far down as 3½ miles, there are more species of coral in the deep than on the shallow tropical reefs.
The deep may be full of alien-like creatures, but we are more closely connected to it than we ever thought possible .
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thanks to great ocean currents.
These currents begin in the frozen poles.
Antarctica.
Here, the surface waters are so cold and heavy that they sink .
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and that creates immense rivers of water that flow into the deep.
This is the start of a giant network of currents .
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that flow from the poles to the tropics and back again .
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linking every ocean.
These currents are in fact crucial to the wellbeing of our planet.
They distribute the sun's heat, maintaining a favourable climate for life on Earth.
From creating the weather to producing oxygen, the seas keep our world healthy.
But just as we are discovering how dependent we are on the oceans, there are worrying signs that they are warming at a faster rate than ever before in human history.
And nowhere is this more extreme than in the Arctic.
Here, in the past 30 years, the extent of the ice in summer has been reduced by 40%.
This sudden warming, most likely a consequence of human activity, is having a profound impact on its wildlife.
Walruses are among those that are seriously affected.
LOW GROWLING The sea ice is retreating from much of the walrus's traditional range, so they now have to haul out on dry land.
But a herd of hundreds of quarrelsome mothers, some weighing almost a ton, is not an ideal nursery.
THEY GRUNT AND GROWL Walruses on land stick together for good reason.
Polar bears.
A full-grown male walrus is gigantic - too big for even a polar bear to tackle.
So the bear is looking for a walrus baby.
THEY SNARL The scent of the bear spreads alarm through the colony.
The walruses retreat into the sea.
The bear knows it won't be able to catch them there.
But she too has young ones to feed.
What is a mother to do? WALRUS BARKS A mother walrus still needs to find a place where her young can rest.
A melting iceberg might do.
But she is not the first to find this one.
Suitable places are already taken.
Other mothers don't want to share.
They too need a patch of ice where they can protect their young.
The desperate mother has no choice but to barge her way in.
THEY GROWL AND SNARL So, this time, everyone loses.
Finding the right place on these melting shores gets harder and harder.
Solving these problems together helps create a bond so strong that the mother will stay in contact with her young for the rest of her life.
But who knows now what their future will be? As we understand more about the complexity of the lives of sea creatures, so we begin to appreciate the fragility of their home.
We are at a unique stage in our history.
Never before have we had such an awareness of what we are doing to the planet, and never before have we had the power to do something about that.
Surely we have a responsibility to care for our Blue Planet.
The future of humanity, and indeed all life on Earth, now depends on us.
To find out more about our oceans with this free poster, call .
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or go to .
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and follow the links to the Open University.