(THEME MUSIC PLAYING)
DAVID ATTENBOROUGH: The world's greatest wilderness,
the open ocean.
It covers over half the surface of our planet.
Here, there is nowhere to hide
and little to eat.
(GURGLING)
It's the marine equivalent of a desert.
(PULSE SOUNDS AND CLICKING)
And patrolling this desert, spinner dolphins.
They stick together.
In a super pod, 5,000-strong.
That maximises their chances of finding something to eat.
Like all who live here,
they must go to extraordinary lengths
to make their home in the big blue.
(GURGLING)
There are rare moments
when these empty seas can explode 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.
(DRAMATIC MUSIC PLAYING)
For the dolphins, this would be a bonanza.
(DOLPHINS CLICKING)
They have located the shoal using their echo-sounding calls.
(DOLPHINS CLICKING)
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 CLICKING)
(DRAMATIC MUSIC PLAYING)
They swim beneath the shoal, pinning it to the surface
and forcing the lanternfish to pack more closely together.
(DOLPHINS SQUEAKING AND CLICKING)
And now the sea begins to boil.
The tuna charge into the shoal at over 40 miles an hour.
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 in frequent.
Whilst the dolphins perform great feats of endurance,
others are driven to even greater extremes
to find food in this ocean desert.
(GURGLING)
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.
(CLICKING)
One has a calf.
It's about two weeks old, but still dependent on its mother's milk.
It's hungry.
(CALF CLICKING)
It communicates with its mother using a pattern of clicks.
(CLICKING)
But its mother slumbers on.
(CLICKING CONTINUES)
The calf, covered in suckerfish,
of which it can't yet rid itself,
has to be patient.
(CONTINUES CLICKING)
(LOUD SPLASH)
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...
(LOUD RUSTLING)
...to saturate their blood with oxygen.
Then, down they go.
(CLICKING)
This entire family dives together in search of squid.
The 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
touching her frequently
as if for reassurance.
(RAPID CLICKING)
(CLICKING)
About 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.
(CLICKING)
The mother changes her calls
into a series of louder and more rapid clicks.
(RAPID CLICKING)
She's now using sonar to hunt down shoals of squid.
(VERY RAPID CLICKING)
At 800 metres, a burst of clicks.
(VERY FAST CLICKING)
Then, silence.
She's made a catch.
The hunters could be away for as much as an hour.
(CLICKING)
Finally, the mother returns from the deep
with her stomach full of squid.
(CLICKING)
After a long wait,
this hungry calf can take some milk.
(CLICKING)
It's one of the richest produced by any mammal.
And the calf guzzles a bathful of it a day.
It maybe six years before a calf masters the art of deep diving
and is able to find food for itself.
(CLICKING)
The emptiness of the big blue is what makes life so hard for hunters.
But it's this emptiness
that makes it comparatively safe for prey.
A baby turtle, hatchedjust days ago,
is leaving the crowded, dangerous waters of the coast,
and heading for the open ocean.
Only recently have we begun to solve the mystery
of where baby turtles disappear to in their early years.
To start with, they fill their little stomachs with plankton.
But soon, they need something more substantial.
Hundreds of miles offshore, in every ocean,
there are communities of young castaways.
(WHIMSICAL MUSIC PLAYING)
So, anything that floats attracts them.
A log.
It may have been at sea for several years,
and it has already become the centre of a small community.
Young pufferfish are here for the same reason.
The floating log is just the kind of refuge
this young turtle has been looking for.
Here, there's not only seaweed on which to graze,
but barnacles.
But it's important to stay undercover.
A young ocean-going silky shark is here too.
It's learning what tastes good,
and what doesn't.
We now know that many young turtles
stay in such places for several years
until adulthood.
Even if it means facing the full force of the high seas.
(LOW RUMBLING)
The sun, beating down on the deep blue,
warms the surface waters so that they evaporate.
(LOW RUMBLING)
As the vapour rises, it condenses into clouds.
They rapidly build into gigantic burgeoning towers,
which eventually generate violent storms,
some a thousand miles across.
(WIND HOWLING)
(WAVES CRASHING LOUDLY)
Hurricane force winds sweep across the open ocean,
building waves that could rise to 30 metres tall.
Out here, ships have been known to sink without trace.
(WAVES CRASHING LOUDLY)
One hundred and thirty million containers
are shipped across the oceans every year.
And on average, four of them fall into the sea every day.
(RAINFALL PATTERING)
(GURGLING)
In 1992,
a few were lost that contained a consignment of bath toys,
including 7,000 plastic ducks like these.
They started their travels a thousand miles off Alaska.
Some drifted right across the Pacific Ocean,
and reached Australia.
Others were carried north,
and landed on shores between Russia and Alaska.
They even found their way into the high Arctic.
One duck, having been at sea for 15 years,
and crossing three oceans,
eventually landed on the west coast of Scotland.
Their travels vividly illustrate
how a network of currents connects all our oceans
into one gigantic circulatory system.
Many of the inhabitants of the big blue
rely on these currents to carry them to feeding grounds.
(LOW GURGLING)
The blue shark.
It travels over 5,000 miles a year,
riding on the currents,
supported by its broad wing-shaped fins.
This one may not have eaten for two months.
But the currents can carry promising traces of fatty oils
from many miles away
and will lead it to its next meal.
(LOW GURGLING)
After days of travel, the smell of food gets stronger.
A dead whale, recently struck by a ship.
This could be a real feast,
but the blue shark must be cautious.
Great white sharks,
ten times heavier than the blue,
are highly possessive around a whale carcass.
Great whites are eager to feed on energy-rich whale blubber,
which we now know forms a major part of their diet.
Once the great white has had its fill,
smaller sharks, like the blue shark,
tackle what's left of the carcass.
As the oils from this dead whale spread more widely,
more and more blue sharks appear.
Within days, the carcass will be stripped of its blubber.
Then, no longer kept buoyant by its oil,
it will sink into the depths below.
The blue, with its reserves of fat replenished,
can now survive for another two months without eating.
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.
Some can grow to a metre, even two metres across.
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 lifeforms 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,
propped by a vertical membrane.
With that serving as a sail,
it maintains a steady course through the waves.
(BIRD SQWUAKING)
Long threads trail behind it,
some as much as 30 metres long.
Each is armed with many thousands of stinging cells.
A single tentacle could kill a fish,
or, in rare cases, a human.
But among its lethal tentacles,
lurks a man o' war fish
that feeds by nibbling them.
Whilst this fish has some resistance to the stings,
it must still be extremely careful.
Most other fish are not so lucky.
A tentacle has caught this one, and reels it in.
(SWISHES)
It's already paralysed.
Specialised muscular tentacles
transfer the victim to others that digest the catch,
liquefying it with powerful chemicals.
Eventually all that is left
is a scaly husk.
This voracious man o' war
may collect over a hundred small fish in a day.
(BIRD SQWUAKING)
For the most part, the big blue seems featureless.
A place where the winds blow, uninterrupted by land.
But beneath the surface,
there are long mountain ranges, deep trenches,
and isolated volcanic peaks
that make it far more varied than the human eye can see.
We're only just discovering in any detail
how the inhabitants of the big blue exploit that.
A lonely whale shark
on a special journey.
She is as long as a small aircraft,
and she weighs over 20 tonnes.
Like many sharks, she does not lay eggs,
but gives birth to live young.
She carries up to 300 of them
in her swollen belly.
She may be the biggest fish in the sea,
but the place where whale sharks give birth has not yet been found.
Today, however, we may be a step closer to solving this mystery.
We have known that great numbers of whale sharks,
at certain times of the year,
appear around the Galápagos Islands.
Here they assemble around a tiny islet
that rises abruptly from particularly deep water.
It's known as Darwin Island.
(BIRDS SCREECHING)
Here, swirling currents bring out nutrients from the deep,
so enriching these waters
that they attract great concentrations of fish
from far and wide.
Thousands of hammerhead sharks also assemble here.
They are nearly all female.
They, too, it seems, have come here to breed.
The whale shark receives an extraordinary welcome.
Silky sharks, themselves three metres long,
bounce against her rough skin,
perhaps to scrape off any parasites they might have.
These sharks could be a danger to any newly-born young.
So, perhaps to avoid them,
the whale shark dives
down to around 600 metres.
And there, she may release her young.
In these great depths,
away from the predators that hunt in the waters above,
and with abundant food,
her babies could grow and eventually disperse.
No one, it is true,
has ever seen young ones in these little-visited depths.
But the fact that hundreds of expectant whale sharks
come here every year,
is strong evidence that somewhere here
lies the nursery of the biggest fish in the sea.
There are almost 30,000 sizeable islands
scattered across the world's oceans.
One of them is South Georgia.
An ideal place for those ocean-dwellers
who are compelled to land in order to breed.
The wandering albatross.
It may spend as much as a year continuously at sea,
searching for food,
gliding on wings that are three and a half metres across.
The biggest of any living bird.
(ALBATROSS SHRIEKING)
(BIRDS SCREECHING)
The entire world population
of 16,000 wanderers nest on South Georgia
and half a dozen or so of the other smaller islands
that lie in the Southern Ocean.
It's spring.
And this bird is returning to the nest site it has always used.
(ALBATROSS CROAKING)
(CALLING LOUDLY)
(ALBATROSS GRUNTING)
Its lifelong partner is already here.
(BOTH GRUNTING)
In South Georgia,
individual birds have been studied for their entire lives
revealing that older pairs in their late thirties
will go to extraordinary lengths
to give their young the best possible start in life.
(BOTH CALLING)
(ALBATROSS SHRIEKING)
This chick is now several weeks old,
but still has its warm, downy coat.
(LOW GRUNTING)
The chick will need a regular supply of regurgitated fish and squid.
With food so scarce in the open ocean,
both parents may have to scour thousands of square miles
just to provide enough for one meal.
(SQUAWKS LOUDLY)
(BIRD SQUAWKING)
Ageing parents struggle on all through the Antarctic winter,
to raise a chick that is big, strong and healthy.
(SCREECHING)
After some 130 days,
the youngster begins to replace its down with flight feathers.
(CROAKING)
Finally, nine months after their egg was laid,
this chick is ready to leave.
(CHIRPS)
(LOW CROAKING)
(SQUAWKING)
Of all the chicks they've reared in recent years,
such a favoured chick will have the best chance of survival.
But it will also be their last.
(LOW CROAKING)
Elderly parents never recover from their exertions.
They will soon leave this island,
never to be seen again.
(SOFT RUSTLING)
Surviving in the open ocean
has always tested animals to the limit.
But today, they face a new, additional threat.
Plastic.
Just over a hundred years ago,
we invented a wonderful new material
that could be moulded into all kinds of shapes.
And we took great trouble to ensure
that it was hard-wearing, waterproof,
and virtually indestructible.
Now, every year,
we dump around eight million tonnes of it into the sea.
Here, it entangles and drowns vast numbers of marine creatures.
But it has even more widespread and far-reaching consequences.
(HIGH-PITCHED WHISTLING)
A pod of short-finned pilot whales.
(HIGH-PITCHED WHISTLING)
They live together in, what are perhaps,
the most closely-knit of families in the whole ocean.
(HIGH-PITCHED WHISTLING)
Today, in the Atlantic waters off Europe, as elsewhere,
they have to share the ocean with plastic.
(WHISTLING AND CALLING)
A mother is holding her new-born young.
It's dead.
She is reluctant to let it go
and has been carrying it around for many days.
As plastic breaks down, it combines with other pollutants
that are consumed by vast numbers of marine creatures.
In top predators like these,
the toxic chemicals can build up to lethal levels.
It's possible her calf may have been poisoned
by her own contaminated milk.
Pilot whales have big brains.
They can certainly experience emotions.
Judging from the behaviour of the adults,
the loss of the infant has affected the entire family.
(CLICKING)
Unless the flow of plastics into the world's oceans is reduced,
marine life will be poisoned by them for many centuries to come.
The creatures that live in the big blue
are, perhaps, more remote than any animals on the planet.
But not remote enough, it seems,
to escape the effects of what we are doing to their world.
(DRAMATIC MUSIC PLAYING)
The biggest challenge of filming
in the vastness of the open ocean
is to find your subject.
(CLICKING)
And the Blue Planet team
wanted to film one of the most elusive of them all.
The rarely-witnessed
"boiling sea."
Until now, this feeding frenzy
has been the stuff of legends.
(BIRDS SCREECHING)
After some promising sightings off the north east coast of Australia,
the team heads out to investigate.
We know it's a phenomenon
and we know it's out there, the scientists have documented it.
The fishermen have told us about it. So we know it's happening,
but no one has been crazy enough
to attempt to go out there and actually film it
except for us.
The team start their search
a hundred miles out in the Pacific Ocean.
The reason it's called the "boiling sea"
is that the tuna are actually coming out of the water
and attacking lanternfish, and it creates a lot of white water.
To film the "boiling seas",
the team must first find a large shoal of bait fish,
most likely to be lanternfish
rising to the surface at night to spawn.
A few days out, Adrian thinks he may have spotted
a giant shoal on the echo-sounder.
What we're seeing is a very, very dense layer
at about 200 metres water-depth.
And so, the fact that we have got this
would suggest that we have a very deep and dense, um, layer of fish.
(MOTOR WHIRRING)
One of the best ways to film untouched depths in the open ocean
is to use an ROV,
a Remotely Operated Vehicle,
carrying a light-sensitive camera.
But working with such heavy equipment in the high seas
is a risky operation.
(METALLIC CLANG AND THUD)
(LOUD WHIRRING)
Fortunately, a team of technicians is on hand,
and 24 hours later, they're ready to re-launch.
Adrian drops them on top of what he hopes
is a large shoal of lanternfish.
Good news is we've just put the ROV down.
We're down at 250 metres,
which means we've gone to almost the end of the cable,
and nothing's blown up, so we're back in business.
But there's almost nothing there.
Just a thick layer of plankton.
Over the next three weeks, they don't find a single lanternfish.
This trip is the perfect illustration
of why we know so little about the ocean.
We came out looking for something,
we've searched and searched and searched,
and we still haven't found it
even with every single tool you could wish for.
As it turned out,
the team had been filming at the very start of El Niño,
an unpredictable climactic event
when sea temperatures can suddenly rise
and disrupt the spawning behaviour of fish.
It would be 18 months before conditions would improve
and the team could continue their quest.
The other side of the Pacific Ocean, off Costa Rica.
This time, rather than searching for their prey,
the team are looking for their predators.
(SQUEAKING)
(CLICKING)
(SQUEAKING)
But in the endless blue,
even finding a massive pod of dolphins isn't easy.
(WHIRRING)
Twenty miles offshore,
series producer, Mark Brownlow,
leads an aerial filming team
scanning thousands of square miles of ocean.
But there's not a dolphin in sight.
Day three, no spinner dolphins.
I'm worried now.
Finally, after ten days on the open ocean,
they get their reward.
Okay, go big.
- ALL: (CHEERING) - MARK: Yes!
We did it!
With the dolphins in sight, the dive team race to intercept them.
MAN: Spinners, look.
The plan is to film
the dolphins' feeding frenzy from underwater.
Several hundred dolphins jumping all over the place,
it looks like this could be it.
They catch up with the dolphins.
But they're too late.
Oh, dear.
RACHEL: Nothing, Rog?
Nothing. Just fish scales and bones.
It's like turning up at a battle only to see all the dead bodies left over.
To stand a chance of filming the dolphins feeding,
the dive team need to be more proactive.
Rachel hitches a ride, following them underwater
searching for any clue to where they might go next.
(SQUEAKING)
Finally,
after three weeks of searching,
the dive team catch a huge feeding event.
A massive shoal of lanternfish
being rounded up by hundreds of spinner dolphins.
ROGER: That was incredibly intense.
A very large bait ball
spread over probably the size of a football field.
Fins coming in all over your shoulder, over your head.
It was incredible.
For the first time,
the aerial team can record the epic scale of this spectacle.
You know, we heard these stories of "boiling seas", but it's real.
They're huge.
The vastness of the ocean wilderness
made capturing this extraordinary event a great challenge.
But this is the reward.
A moment of unparallelled drama
in the immense expanse of the big blue.
Next time, we journey into the bountiful green sea.
These are enchanted worlds,
home to strange creatures...
(CRUNCHING)
... where only the most ingenious will triumph.
(THEME MUSIC PLAYING)