Great Barrier Reef with David Attenborough

I'm here, surrounded by one of nature's greatest wonders.

A living structure so enormous, it can be seen from space.

The Great Barrier Reef.

Home to one of the most extraordinary communities of animals on the planet.

'I've been fascinated by it for almost 60 years.'

Here, unknown species are still being found.

And scientists are making astonishing discoveries

about the creatures that we thought we knew.

'In this series, our research vessel, the Alucia,

'will allow us to explore the reef as never before.'

Using the latest technology, I'll visit its mysterious depths.

Nobody has ever dived as deep as this before on the Great Barrier Reef.

I'll learn of its surprising origins.

And discover how this wonderfully diverse community

has been created by some of the very smallest creatures on the reef.

But visited by some of the most impressive animals on the planet.

It's an ecosystem like no other.

Vital to our oceans.

And surprisingly, we are still uncovering its many secrets.

The Great Barrier Reef lies on Australia's north-east coast.

It's 1,400 miles long...

...and at its widest, 150 miles across.

It consists of almost 3,000 individual coral reefs...

...and 900 islands.

And for me, it's truly

one of the most extraordinary places on the planet.

People say to me,

"What was the most magical thing you ever saw in your life?

"What was the most magical moment in your career as a naturalist?"

And I always say, the first time I put on a mask

and went below the surface

and moved in three dimensions just with a flick of my fin

and suddenly saw all these amazingly multicoloured things

living in communities right there.

Just astounding things.

Unforgettable beauty.

I first came to the Barrier Reef nearly 60 years ago.

And I remember very clearly how amazed I was

to see such a complexity of life.

But today, we have ways of looking at the reef,

technical ways, which we never had before

and give us a completely new vision of this wonderful place,

which is surely one of the greatest treasures of the natural world.

'Now I've returned.

'And taking me on this journey is the Alucia,

'a 56-metre state-of-the-art research and exploration vessel.

'For this expedition, we've been granted unprecedented access

'to some of the most remote corners of the Great Barrier Reef.'

Onboard is a team of experts.

And at our disposal, all the latest technology.

Our mission is to reveal a hidden world

and to complete a series of dives

that have never before been attempted on the Great Barrier Reef.

But to do that, we have had to bring in a very special piece of equipment.

This is a Triton submarine.

The very latest in submersible technology.

And the first of its kind to be brought to these waters.

The submersible's captain, Buck Taylor, will lead the dive team.

With 2,000 dives under his belt, his expertise is unparalleled.

While our film crew rigs the submersible

with no fewer than eight cameras,

Buck gathers the rest of the team together

to brief us on the dives ahead.

"Welcome to the MV Alucia submersible team..."

'The submersible offers spectacular filming opportunities,

'but it's not without its dangers.'

Coming from the rescue background,

I've been in a submersible up to my waist in water,

I've had a fire in a submersible.

"No smoking, smoking materials..."

'As well as these hazards, Buck is also obliged to raise

'one of the more intimate limitations of submersible life.'

We do have facilities of a toilet onboard.

Obviously, because it's quite confined, it's not very discrete,

so we do have some towels out that we can hold up around you.

It's quite interesting trying to explain about going to the toilet

in a three-man submersible in a sort of sphere

that's less than two metres diameter. It's quite intimate.

He was six foot three... LAUGHTER

We've got cameras pointing from every direction.

Good. Thank you.

Thanks very much. I'm looking forward to it a lot.

The Alucia's first mission

is to take us to the Barrier's stunning ribbon reefs

in the north of its extensive range.

It's an area of outstanding natural beauty

and the perfect place to begin our explorations.

The story of the Great Barrier Reef

starts with its most important inhabitant, the coral itself.

Hidden inside these branching structures

are the thousands of tiny creatures that build these reefs.

And they have an enormous claim to fame.

Together, they've built the largest living structure on earth.

But these fascinating coral creatures are only active at night.

So to capture their behaviour,

we'll need to do something I've never done before.

Tonight, a team of specialist divers, scientists

and programme-makers, like myself,

have gathered together to have a closer look and a longer look

at the reef at night than perhaps has ever been possible.

When I came here 60 years ago,

the idea of a night dive was almost inconceivable.

It seemed to me, a beginner, to be far too dangerous.

But now, technology is going to help me.

'Once I'm in, it's over to Buck and the support team,

'who remain onboard the Alucia,

'to make sure everything goes smoothly.'

INDISTINCT RADIO

'They've spent months preparing for this moment.'

SIREN WAILS

'Our submersible, known to the crew as the Nadir,

'has, of course, made dives like this all over the world.

'She's descended to the deepest part of the oceans,

'but she's never visited the Barrier Reef.

'It's a first for all of us.

'But before we can go anywhere, we'll need to position the Nadir

'at a safe distance from the Alucia.

'It's a substantial operation,

'but finally, we're ready to get underway.'

S.O. Nadir, just approaching the buoy. Am I clear to vent?

"Roger, Nadir. You are clear to vent, clear to vent.

"Have a good dive, guys."

'Sinking beneath the waves is a very surreal experience.

'Your first instinct is to hold your breath.

'At night, the reef is a ghostly world.

'Tiny shrimp-like creatures dance in the lights.'

Look at that! Wow!

'With little light, there is a lot less colour,

'but this is still a very magical place.'

Ah! There's something! My first fish!

'Our submersible will eventually take us to depths of 300 metres.

'Now, we're only 30 metres down,

'but that's exciting enough for a start.'

In these dark waters, Buck needs to be careful

as we move around the front of the reef.

Coral reefs are sometimes described as marine cities.

And the comparison is indeed a good one.

We're here to take a closer look at the reef's architecture.

Its coral buildings.

There are more than 450 different species of hard coral.

The plant-like structures we can see are actually made of limestone.

And living inside are thousands of highly industrious little animals

called coral polyps.

At night, the water around the reef

becomes filled with clouds of tiny microorganisms

called the zooplankton.

And that's what the corals eat.

The coral polyps themselves emerge from their stony skeleton

and start groping in the water with their tentacles.

To see just what they're doing, we need specialised cameras.

The coral polyps never leave the safety of their limestone homes,

even at night.

If something edible comes within reach,

the polyps fire the microscopic harpoons that line their tentacles.

The prey is stunned or killed and then pulled into the polyp's mouth.

When you can't leave your home, it pays to be accurate.

The coral's stinging armoury isn't used only for collecting food.

They also use it to fight.

Because, as has been discovered only comparatively recently,

corals, like many animals that live on land,

are extremely territorial.

But in order to see the battles,

you have to speed up time.

The polyps of each colony collaborate to defend their patch.

As in any big city, space is precious.

If a rival grows too close, there will be trouble.

These fights can last for hours.

The competition is fierce

as the coral colonies jostle with one another

for the best feeding sites.

When they're not locked in battle, the corals have work to do.

'They must extract calcium carbonate from the surrounding seawater

'and with it, build their homes.'

Each coral species has its own particular way of building.

And together, they eventually create the huge reefs

that provide homes for all kinds of other, much larger creatures.

At night, the reef seems like an extraterrestrial world.

But down here, we are the aliens.

And here comes a turtle!

Attracted by our lights.

Come on!

Coming straight to us.

Isn't that great!

'Coming face-to-face with a green turtle

'in this setting is a rare privilege,

'but its presence here, along with all the other reef residents,

'is only made possible thanks to the great coral builders.'

He doesn't look very upset, does he?

It happens all the time on this reef.

It's the perfect end to my first dive.

The time has come for us to make our way back up to the Alucia.

Welcome back, gentlemen.

Diving on a reef at night is a thrilling experience.

What I want to see next is how exactly these tiny coral creatures

have created such a vast and extensive habitat.

To answer that, we'll need to look at the reef

from another angle entirely.

At this height, you can begin to appreciate

the immense size of the Barrier Reef.

It's 2,300 kilometres long, 1,400 miles.