Original subtitles

There are more animals in the ocean...

...than anywhere else on Earth.

25 years ago,

in The Blue Planet,

we began a journey

beneath the waves.

Now, in this new series, we venture

even further.

Over four years,

we have launched more than 100 expeditions

to every corner of the globe...

...filming underwater for thousands of hours...

...to reveal the wonders of the ocean

as never before.

In a voyage around the planet...

...we will uncover life...

...that is more surprising...

...more intelligent...

...and even more precious than we ever realised.

This is Blue Planet III.

The northern tip of Australia.

Here lives a young tawny nurse shark.

It's calm,

docile and has tiny teeth.

More puppy than predator.

Receptors in its skin detect movement...

...and, with a mouth like a vacuum cleaner,

it sucks up sand in search of scraps.

Pickings are slim.

But vibrations in the water

tell it that something is out there.

Among the plains of sand,

there are oases of life...

...reefs where millions of herring and silversides gather.

A rich opportunity for hunters.

But in crystal-clear waters,

a slow shark is easily noticed.

What's more, there is competition.

Lemon sharks and blacktip sharks.

Fast...

...powerful

and built for the chase.

Tawnies are no match for their big-toothed cousins.

But there may be another option.

Moving into the shallows, it appears to take a nap.

Others have the same idea.

Tawnies for miles around are headed to the same spot.

Sharks are often solitary.

But here, in barely a metre of water...

...more than 40 now huddle together.

As the tide falls,

the fish congregate on the shoreline.

For four hours, the sharks stay still.

And the fish gather around them.

All it takes

is for one shark to stir.

Something remarkable begins.

In a rare display of coordination...

...together they drive the fish

out of the water and onto the beach.

They can now suck them in by the mouthful.

This is one of the only places on Earth

where sharks appear to hunt as a team.

In the tropical seas,

there is still so much to discover.

Stretching in a belt around the equator

from Africa to Indonesia and beyond,

these waters have been bathed in year-round sunlight

for millions of years...

...giving rise to the richest seas on Earth.

There are more species here

than anywhere else in the ocean.

In the tropics, life thrives in hot spots.

Shark Bay, Western Australia...

...home to one of the greatest concentrations

of dolphins on the planet.

DOLPHINS WHISTLE AND CHIRP

To get ahead in this crowded world takes great ingenuity.

This bottlenose dolphin

has lived here for over 40 years.

Heavily pregnant, she must eat 10kg of fish a day.

But experience has taught her

that there are opportunities here...

...tiny, isolated patches of reef known as bommies.

At the first sign of trouble,

the fish retreat to safety...

...beyond her reach.

But she has a clever solution.

Dolphins here have been seen carrying sea sponges...

...originally thought to protect their snout

when foraging on the seabed.

Only now do we know

the reason is far more complicated.

She takes the sponge back to the bommie...

...and carefully, deliberately

places it in just the right position.

She backs off...

...far enough for the fish to relax.

And with a burst of speed, she sends them fleeing...

...only to find their hiding place plugged

by the sea sponge.

It is her first meal of the day.

In an area the size of Manhattan...

...she seems to have a map in her mind...

...of where to find sponges...

...and the best bommies.

It's one of the most sophisticated examples

of trap setting in the animal kingdom.

Only a select few have learnt this skill...

...a cultural tradition passed down from mother to calf...

...that gives these dolphins the edge

in this competitive world.

Abundant sunlight and clear water

have allowed one of the planet's most ancient hot spots

to flourish.

Coral reefs.

They owe their existence to tiny creatures,

many no bigger than a pinhead.

A coral polyp.

There are millions of these jelly-like animals

on every reef.

Powered by the sun, they absorb minerals

from sea water and turn them into stone...

...the foundation of all reefs.

Over millennia, tiny coral polyps

have built the largest living structures on our planet...

...some thousands of miles long.

These solar-powered cities

are home to a quarter of all the species

that live in the ocean.

Between Africa and Arabia

lies a unique reef system in the Red Sea...

...with more than 300 different species of coral

and over 1,200 species of fish.

For a predator like this burly grouper,

this should be an all-you-can-eat buffet.

But the coral reef is a fortress

with plenty of places to hide.

The grouper can see them...

...but is just too big to get inside.

Time to recruit heavyweight help.

A Maori wrasse.

Almost two metres long, 20 stone of solid muscle.

But how to catch his attention?

First, find the prey...

...then signal with a headstand...

...pointing the way to where the potential meal is hiding.

Message received.

As the wrasse smashes in...

...the grouper guards the exits.

But the fish are only driven deeper inside.

Brute force isn't working.

Perhaps more finesse is required.

There is a hunter...

...that thrives in the shadows.

The moray eel is able to get into the narrowest cracks.

But he will need some convincing.

Fortunately, this grouper is a master linguist...

...and can communicate with two different species.

A shimmy here...

...and a twitch over there...

...and the eel responds.

Time to hunt.

The grouper chases the fish in from above...

...while the eel corners them from below.

Success for the grouper.

And for the eel.

The grouper is five times more likely to catch dinner

when hunting with others.

As daylight fades, the bustling reef transforms.

Now the night shift stirs.

Among them, some unexpected villains.

In the tropical waters of Indonesia,

a pair of harlequin shrimp.

A venomous lionfish should be dangerous.

But the shrimp seem afraid of nothing.

Tonight, this dastardly duo...

...are intent on stealing a meal.

And harlequins have a taste for something rather odd.

Starfish.

At 20 times their size,

this one is too big.

This smaller starfish

is an easier target.

Each arm is levered free.

But it's not easy to shift.

Now it will be nearly impossible

to get it back to their lair.

What is more, starfish are quick on their feet.

Only a pair working together

can pin one down.

Time for a new plan.

A bizarre tug-of-war...

...forcing the starfish to relinquish its arm.

As day breaks,

these shrimp stash the limb in their lair.

They will feast on it for several days.

The starfish can grow another arm...

...just in time for the shrimp to restock their larder.

Coral reefs cover less than 1% of the tropical seafloor.

Beyond them,

there is mainly sand and mud...

...a vast, featureless part of the world,

seemingly devoid of life.

But for some,

this calm sanctuary is exactly what they're after.

This humpback whale

has come here from Antarctica almost every year of her life

to socialise and breed.

But this time, something is wrong.

Perhaps she's sick

or has been weakened by her long journey.

We will never know why,

but she is dying.

Hundreds of sharks have gathered...

...apparently waiting for her time to pass.

By the next morning, her story has finished.

In mere hours,

her body has become sustenance for countless others.

In life, she crossed oceans to feed in more fertile waters.

In death,

she brings these nutrients to the emptiest parts

of the tropical seas...

...a fleeting oasis in a seemingly barren world.

Scattered throughout the tropics, over 50,000 islands

attract sea creatures from far and wide.

220 miles from the coast of Brazil

lies Fernando de Noronha.

For green sea turtles, it's an irresistible draw.

Lush seaweed coats the rocks...

...food for this youngster.

And she's not alone.

Hundreds of others come to feed here.

Other visitors are drawn to the island, too.

A lucky escape.

Tiger sharks are reluctant to swim

in very shallow water.

But there is little food here for a turtle.

There is only one option.

Venture back to the deeper waters.

Sharks detect prey

by sensing movement near the surface.

The seafloor is safer.

About every 30 minutes or so...

...they must breathe.

Turtles can't outswim sharks.

But they do have armour.

By turning quickly...

...their shell becomes a shield.

The shallows normally offer safety.

But this shark is unrelenting.

Only when the turtle reaches the edge of the water

does the shark finally give up.

Many bear the signs of such a near miss.

But the chance to feast on luscious seaweed

is worth the risk.

Islands provide essential feeding grounds.

But some tropical habitats offer much more.

Sea meadows.

Where waters are sheltered and shallow,

sea grass grows in abundance.

Vital to life on the planet,

it generates enough oxygen daily to sustain

1.5 billion people.

They're also a critical home for marine life...

...including herds of herbivores.

A dugong, weighing nearly half a tonne,

with a taste for grass.

It's no surprise that they're known as sea cows.

The fibrous blades are tough to digest,

so he feeds for ten hours a day.

Not all share his enthusiasm

for hard graft.

Remora fish are freeloaders,

and they know a dugong is key to an easy meal.

After feasting for hours, an after-dinner nap is inevitable.

The remora sneak in...

...latching on with a head-mounted suction cup...

...for a banquet of dead skin and parasites.

But their tickling has woken the giant.

He wants rid of them.

All clear?

Not a chance.

The dugong has more to offer...

...from an unusual source.

A small bubble of flatulence...

...signals the main course is imminent.

Dugong dung.

Finally, the dugong can feed in peace.

For now.

On some special coastlines in the tropics...

...forests grow from the ocean.

Mangroves.

The longest stretch is on Brazil's northern shore.

Aerial roots trap sediments and leaves,

capturing 50 times as much carbon as the same area

of rainforest.

As the tide retreats,

it leaves behind a rich layer of mud.

A brief opportunity...

...for a male fiddler crab...

...to acquire a mate.

At half his body weight,

his claw should be irresistible.

But females seem more interested

in food than flirtation.

Maybe a beckoning wave

could do the trick.

But there's stiff competition.

If a crab won't back down...

...they must duel.

But this could be a perilous distraction.

The females run for cover.

That's one way to overcome your opponent.

Scarlet ibis feathers

are coloured crimson by pigments

from the bodies of their victims.

Time to make a break for it.

Safe in here...

...surely.

But this pursuer has a long beak for a reason.

As the tide begins to rise,

the ibis are forced to leave the mudflats.

A quick glance to check the coast is clear...

...and it's back to courting.

With most males still cowering...

...it's easier to get female attention.

Just in time before the rising tide covers the burrow.

In a few exceptional places...

...the different tropical habitats

all flourish side by side.

Mangroves can filter the water,

which helps the sea grass and reefs to thrive...

...as it does here

in the Coral Triangle of Southeast Asia.

This is the richest marine habitat on the planet...

...home to one of the tropics' most well-known inhabitants.

Clownfish.

Immune to its stinging tentacles,

this magnificent anemone is their shelter...

...their nursery...

...their entire world.

For millions of years,

clownfish have relied on anemones for survival.

But the tropics are now changing rapidly.

During the filming of this series, their reef experienced

an unprecedented underwater heatwave.

Corals depend on microscopic algae living within them.

They convert sunlight into sugar,

much as plants do.

But when waters become too warm...

...the algae turn toxic.

The coral ejects them.

Having lost their main source of nutrition...

...they begin to starve...

...and bleach.

The clownfishes' anemone also bleaches.

It is alive, but only just.

Without it,

the clownfish family will almost certainly be eaten.

So they get to work.

They carefully remove debris...

...and clean the tentacle tips,

allowing the anemone to capture passing plankton.

And by fanning with their fins,

they draw in oxygen-rich water, giving it a chance to breathe.

After more than a month, the clownfish are exhausted.

Predators are closing in.

But in the air above,

the winds are shifting...

...bringing cooler waters.

A stroke of luck.

Over the coming weeks, the heat eases.

Slowly, tentacle by tentacle,

anemones on this reef start to recover.

The clownfishes' intensive care has helped keep it alive.

But across the tropics, there were multiple heatwaves.

Countless reefs bleached...

...and died.

Some corals have already started to recolonise.

But if the climate keeps warming at current rates,

reefs won't have time to fully recover.

And it's predicted that in the next 25 years,

coral reefs as we know them could be gone.

These tiny fish helped to protect their home.

Imagine what we could achieve if we all worked together

to protect ours.

It's now more important than ever

to understand our oceans.

So the Blue Planet III team travelled the world,

uncovering many of its secrets.

Producer Yoland Bosiger

and her team were determined to solve a 40-year mystery -

why dolphins in Australia

carry sponges.

This is a behaviour that I've wanted to film

for over a decade,

and it's only now that we have a chance.

What we only see is what we see at the surface,

and we see the dolphin with the sponge.

Nobody's ever actually seen what's going on

at the very bottom, on the seafloor.

It takes over 100 drone flights...

12 o'clock now.

...to finally find what they're looking for.

She got sponge. She got sponge. We're on!

It's right there. Here we go.

Cinematographer Alex Vail attempts to approach

from the water.

Alex!

She's got the sponge on.

But the dolphins keep their distance...

...and the water is murky.

The dolphins just don't seem keen

on us being in the water with them.

They changed direction as soon as I got in.

It's not a promising start.

But drone footage reveals

one dolphin carrying a sponge more than any other.

Simon identifies her from his records...

It's a really great fin

that's got a big chunk out of the leading edge,

as well as a chunk out of the trailing edge.

It's very distinctive.

...known to some as Gambarra.

But Alex will need to earn her trust

if he is to get close enough.

Just under the bow now.

He will have to approach slowly.

But they have company.

BANGS ON SIDE

Guys? Guys, back to the boat.

Tiger sharks.

50 metres out,

just over there.

Nice one. Shark just off that point, guys.

This is called Shark Bay for a reason.

Wow. Look, that's a big shark!

They are keen!

It's now clear

why the dolphins in the bay are so cautious.

I think we might give diving a miss for a little while.

With poor visibility, wary dolphins

and resident sharks,

the team need a new plan.

Now the sharks have gone,

they deploy five remote cameras,

the first of their kind, capable of recording underwater

for over 24 hours.

Stonefish four is recording.

They hope to strike it lucky.

But with over 1,000 hours of remote footage,

there's no dolphin in shot.

So far, we've been out here three weeks

and we've had not a single image.

We're just going to keep trying

and hope that at some point it pays off.

Oh, yeah. Got it. Got it.

Gambarra's got the sponge.

The team begin to notice

a pattern in Gambarra's behaviour.

She's making a beeline to some of

the spots we've seen her previously.

She's visiting the same set of coral bommies

over and over again.

We're really getting a much richer picture

of the way she roams her estate and moves between

preferred foraging areas.

The team now know exactly where to deploy

their underwater cameras.

Yeah. Hello!

CREW LAUGH DELIGHTEDLY

She looks so mischievous, doesn't she?

Hello!

This time, success.

Oh, my God! Oh, that's so good.

The animal obviously knows that the prey species

is looking to escape in that hole,

and it's solved the problem, "How do I block that hole?"

It's more complicated than we originally thought,

so this is really a wonderful discovery.

The remote cameras have captured the very first

underwater images of this complex behaviour.

ALL EXCLAIM

As the underwater cameras continue to deliver...

Oh, my God.

...Alex painstakingly works on gaining Gambarra's trust.

Here we go.

Still there, still in front of him.

And got the sponge.

Oh, yes, what a good dolphin!

Look, she's turning!

And after a month on location,

she finally allows Alex close enough to film her in person.

And I reckon she's placing it.

She's going to place it right next to him. Yes!

Yep, place him there.

This is so good!

I never thought that we would get

in the water near the animals,

but with a gently, gently approach,

she's just come right by the camera ops,

and it's just a phenomenal moment.

I feel like we've been given this really privileged view

into this very special dolphin's life,

and I just hope that she looks after herself

and... really wish her well.

We're going to miss her.

GAMBARRA CLICKS

Next time...

...the open ocean...

...a vast wilderness...

...where life thrives against all odds.

Explore our changing oceans with the Open University's free poster.

To order, call 0300 303 3553,

scan the QR code,

or visit connect.open.ac.uk/blueplanet3.

Into the Deep by Jade & Hans Zimmer