All language subtitles for BBC.Great.Barrier.Reef.with.David.Attenborough.1of3.Builders.1080p.HDTV.x264.AAC.MVGroup.org.eng

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.

COMPUTER: "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.

COMPUTER: "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?

RADIO: "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.

It's the largest living structure
on the planet.

Reefs much like these develop
in the shallow tropical waters

that surround many an island
and continental coast.

But few can match the Great Barrier

in either size or complexity.

So, what is so special about
the north-eastern coast of Australia?

A clue to the answer
lies in the shape of the sea floor.

If we strip away the ocean,

we can reveal the reason why such
extraordinary growth is possible.

The reef has grown on
a very shallow continental shelf.

Beyond which, there is a sudden
and very steep 2,000-metre drop-off.

It stands in waters with
an average depth of just 35 metres.

That's just about as far as sunlight
can penetrate with any strength.

Light is crucially important
to reef-building corals

because they have developed
a special partnership

with microscopic algae -

plants that actually grow
within tissues.

The algae get a safe home

and, like all plants,
when they photosynthesise,

they produce energy.

The coral polyps use this energy
to construct their limestone home.

Together, they've built
an underwater city

on a scale that is almost impossible
to comprehend.

But amazingly, just 10,000 years ago,

there was no coral here at all.

The Great Barrier Reef as we know it
today simply didn't exist.

How and when these coral communities
began

is something scientists have only
recently started to investigate.

Marine geologist, Dr Robin Beaman,

has been leading an ambitious project
to scan the entire reef.

And his data has allowed us
to map the sea floor.

David, this is a three-dimensional
model of the Great Barrier Reef.

In deeper waters,
we tend to use sonar,

in shallow waters, we tend
to use underwater laser beams

to image the sea floor.

'By combining computer modelling
and radiocarbon dating,

'his team have been able
to reconstruct

'the key stages in the development
of the Great Barrier.

'Their research has helped identify
an event

'between 10,000 and 20,000 years ago

'which may explain how
the Great Barrier Reef was formed.

'But surprisingly, scientists are not
the only ones to tell this story.'

Australia's Aboriginal peoples
arrived on this continent

around 50,000 years ago.

They have been telling the story
of how the reef was formed

long before the world's scientists
even knew it existed.

To hear that story, the Alucia
is taking us to Northern Queensland

to meet a community
with a very special connection

to this underwater world.

They are the Gimuy Walubara
Yidinji people.

And they live just outside
the city of Cairns.

This community has dwelt alongside
the reef for thousands of years.

THEY SPEAK YIDINY

And many of their traditions
hark back to those ancient times.

THEY SING IN YIDINY

And one of them tells
how the reef came into existence.

It's a legend that has been passed
down from generation to generation

in the form of a dance.

Tell me the story
that's connected to this dance, sir.

It's part of our law story that's
told to me by my dad, my father,

and was told to him by his father
and his grandfather, as well.

The part of the dance
that really interests me

is the story of Gunyah
and the sacred fish.

The story starts with Gunyah
going out to sea.

And he saw a glitter in the water,
which he thought was a fish.

And when he speared it,

he actually speared our sacred fish,
the stingray.

So the fish got angry
and it started to rise up.

And with its wings,
it made the sea rough

and it caused the sea to rise.

Take us back to the time when
the first human beings arrived here.

What was it like then?

The coastline would have been
very different.

So the coastline would have
been right out here,

on the edge of
the Great Barrier Reef.

The sea level was much lower

and they would have fished
and hunted the coastline.

These were limestone hills

that would have been eucalypts,
marshlands.

There would have been
mangrove swamps.

But roughly 14,000 years ago,

the climate started to
dramatically change.

It was the end of the Ice Age.

And all that water started to
inundate the continental shelf

and start to flood this vast,
flat landscape.

And in one man's lifetime?
Absolutely.

So, people living here
are going to have to retreat?

Absolutely. It would
have been a dramatic time for them.

They would have been
following the coastline

as it prograded
further and further back

as the water was flooding the shelf.

The rate of change was so great
that in these very flat areas here,

the coastline would have moved back
by hundreds of metres every year.

Every year? Every year.

Gosh! That's formidable.

So our story is about
the sea rising.

And there used to be a cliff
further out.

And past the cliff
is where the ocean used to be.

Now, that's really remarkable.

Because Western science is just
beginning to make discoveries

that seem to suggest that the sea,

10,000, 20,000 years ago,
was way, way out there,

which is exactly
what your story says.

Extraordinary. Yes.

A folk memory of an event
that happened all that time ago.

Yeah. And the only way
we can keep it alive

is through our song and our dance.
Yes.

Just to keep that going
through our culture.

So the tradition lives.

Yes. It's wonderful.

'It is truly astounding to think
that this story has survived

'for so many years
and across so many generations.

'And that it coincides with
what scientists are now discovering

'about the age of the Great Barrier.'

The polyps that built the reef
arrived as spawn,

swept here by the ocean currents.

Corals are not new to the planet.

They've been around for at least
500 million years.

The new reefs provided homes
for thousands of animals,

and very quickly, a whole new
community began to establish itself.

Today, the Great Barrier Reef

has one of the most diverse
communities of animals on the planet.

And it's the story of
these remarkable reef residents

that I want to investigate next.

To do that, the Alucia is taking me
north to a very special place.

Lizard Island.

It's one of the 600
continental islands

scattered across
the Great Barrier Reef.

And its shallow lagoon is known for
its exceptional biodiversity.

'With the Alucia
anchored in deeper water,

'a more modest mode of transport
will be needed to reach the shore.

'I first visited Lizard Island
in 1957.

'Then, it was completely uninhabited.

'Little did I know how important
this remote outpost would become

'in helping us to understand
the coral reefs.

'But today, that's exactly
what this remarkable place

'is world-renowned for.'

Here, for the past few decades,
there has been a research station

where scientists can study
continuously and in detail

the full complexity of the community
of animals that makes up the reef.

Every year, Lizard Island hosts
100 different research projects.

Here, scientists are shedding
new light

on the lives of the reefs' residents

and the way in which
this complex community works.

Thanks to their research, we now know
that coral reefs rival rainforests

in the vast numbers of species
they support.

The first question is, where does
all that diversity come from?

Lizard Island reefs
owe their richness

to the special plants that,
in places, fringe the shores.

They link land and sea

and they're vital
to the coral reef community.

They're mangroves.

Taking shelter amongst the roots

are thousands of juvenile fish
of all shapes and sizes.

Many of these little fish
look harmless enough,

but when they grow up,
they will become

some of the most ferocious predators
on the reef.

Indeed, the existence
of these mangrove nurseries

is one of the reasons why
the fish populations of the reef

are among the most varied and richest
in the world.

The mangroves are not only nurseries,
they're playgrounds.

The aim of the game here is to
survive the most vulnerable stage

of any animal's life,
being a juvenile.

Baby turtles...

..rays and even sharks
take refuge here.

These juvenile blacktips
are just a few weeks old.

And only one sixth of the size
they will be

when they make it out on to the reef
as adults.

For the first year of their lives,

the mangroves play a vital role
in keeping them safe.

As infants, they're vulnerable
to predation from larger sharks.

But the tangle of mangrove roots
keeps the big predators out

and stops them making meals
of the youngsters.

When the young are ready,

they will eventually leave this
sheltered world behind

and make their way to the reef
beyond the mangrove roots.

The next challenge will be to find
their place

in one of the most crowded ecosystems
on the planet.

Getting on the property ladder here
is no easy feat.

Which is why one of the reefs'
most celebrated characters

has developed
a very special relationship.

Clownfish deal with the problem
of overcrowding

by sharing space with another
creature, gigantic anemones.

They've formed a relationship
in which both parties benefit.

Anemones have tentacles
that are packed with stinging cells.

Most fish touching one
get a very nasty sting,

but not the clownfish,

thanks to the protective layer
of mucus that covers its body.

The clownfish keeps the anemone
in good health

by removing unwanted parasites.

And in return,
the anemone offers security.

Its stinging cells ward off
the sort of creatures

which would otherwise threaten
the clownfish.

When the time comes for a pair to
breed, that protection will be vital.

A female may lay up to 1,000 eggs

on the rock beneath her anemone home.

As she delicately attaches them,

the male follows closely behind,
fertilising the eggs as he goes.

A week will pass
before the young are ready to emerge.

Hatching only happens at night,

so to record it, we have to use
infrared cameras

in a specialised filming environment.

This is the very first time
that this behaviour has been filmed.

With gentle encouragement
from their father,

the young are helped on their way.

Once the little larvae are set free,
they're on their own.

They'll spend the first few weeks
of their life

developing in the open ocean.

But how will the young clownfish

find their way back to
the coral reefs

after drifting many miles out to sea?

To understand that, we will have
to tune into a sense

we don't normally associate with
this colourful underwater world.

Sound.

Coral reefs are surprisingly
noisy places.

Fish and invertebrates
produce a whole range of clicks

and grunts and snaps.

The healthier the reef, the more
varied and numerous its inhabitants

and the louder this chorus is.

We now know that fish,
just like birds,

vocalise most at dawn and dusk.

Damselfish call to defend
their territory.

GRUNTING

Seahorses click to attract a mate.

CLICKING

Others create a very different
soundscape

simply by carrying out
their daily duties.

SQUAWKING

Parrotfish crunching
through the hard coral

are a constant on the reef.

Fish perceive sound
in two different ways.

Many have internal ears,
but underwater,

they can also feel sound
as a vibration.

The noise is a key indication
that the community is in good shape.

In fact, the louder the noise
on a reef,

the more inviting it is to newcomers.

Newcomers like the young clownfish.

This little male
is no bigger than a button,

but the time has come for him
to find his place in the big city.

At this stage, his swimming abilities
leave something to be desired.

But his hearing is so sensitive,
he can tell over hundreds of metres

if a reef is suitable.

His journey can last days.

The final approach is usually made
at night to avoid predators.

How fish hear and respond to sound
of a healthy coral reef

is a major area of study
here on Lizard Island.

And the scientists have a simple way
of collecting these fish for study.

A light trap, like this one
at Lizard Island,

is one way of assessing
the way that the reef is working.

Like moths to a flame, the young
are attracted by the light.

'By sampling the newest members
of the community,

'scientists can figure out
how far these juvenile fish

'are willing to travel
for a good home.'

In the case of the clownfish,
juveniles have been known to travel

250 miles before they find a reef.

Fortunately, for the majority,
it's usually a much shorter journey.

While they rarely return to
the particular anemone

beside which they hatched,

60% find a new home on the same reef.

For the clownfish and the anemone,
cooperation is the key

to success in this extremely
crowded environment.

Other residents, however, take a very
different approach.

Rather than share their home, they
fiercely defend their territories.

This is a mantis shrimp.

Spotting the competition is
half the battle.

There are many different
species of mantis shrimp

but they all have one
thing in common,

superb vision.

The 400 million-year-old visual
system of the mantis shrimp

is the most complex in the entire
animal kingdom.

Its eyes are mounted on two stalks,
giving it independent vision,

but whereas our eyes produce
binocular vision,

each one of theirs produces three
different images.

Not only that, whereas we have three
photoreceptors in our eyes,

the mantis shrimp has up to 16,
giving it access to

parts of the spectrum that we can't
even see, let alone imagine.

And they can use their amazing
vision to devastating effect.

While some are armed with spears,
others carry clubs.

Many are champion boxers.

They can deliver a punch

that accelerates faster than
a .22 calibre bullet.

These powerful blows are used to
stun their prey

and defend their burrows.

Mantis shrimps are one of the more
house-proud residents on the reef.

In fact, they're compulsive cleaners.

They keep their burrows
meticulously neat.

With all that effort, it's hardly
surprising that they're

fiercely territorial.

In fact, mantis shrimps have
earned themselves

a reputation for being
somewhat ill-tempered.

But scientists have discovered that
there's another side

to these macho males.

This young hopeful is trying to
catch the eye of a potential mate.

He starts by showing
off his paddle-like antennae.

His technique may not be very
impressive to us

but he is, in fact, sending
the female secret signals.

And that is possible
because mantis shrimps can see

and reflect a kind of light that
absolutely no other

creature in the world that we know
of can see...

..including us.

The male's display is a private
invitation for this female to dance.

So far, so good.

She makes her way to the
dance floor.

If the male can impress the female
with his performance,

she will choose him
to father her offspring.

It seems that this male has all
the right moves.

The final phase of courtship,
however, usually takes place

out of sight, within their burrows.

The mantis shrimp is arguably
one of the reefs most colourful

characters and typifies the key
to survival here.

Each resident species has had to
carve out its own particular niche

and that is what has created this
extraordinary diversity.

Here, life can evolve 50% faster
than in other marine environments.

The tiny creatures that have built
this remarkable ecosystem

have created a habitat so complex
that it supports all kinds of life.

But none of the reef's
residents would be here

without one truly
extraordinary event.

It occurs just once a year

and is one of the greatest of all
natural spectacles.

It wasn't until the 1980s that
scientists discovered it,

here on the Great Barrier.

On a few nights of the year

when the conditions are just right,

all along the length of the reef,

corals of many different species
suddenly erupt.

It's the great spawning event

and it's one of the wonders of the
natural world.

It's the one time in the year

when the corals themselves don't
just grow by branching,

but reproduce sexually, and it's
vital for the survival of the reef.

In recent years, we've learned
a great deal

about the many factors that
influenced the moment of spawning.

But even though we know it occurs
within days of the full moon in

October or November, the trigger that
starts it all is still a mystery.

The light of the moon is, perhaps,
the most influential,

but there are many other factors,

including the temperature of the
water and the state of the tides.

And as the moment approaches,

all along the length of the reef,

there's a mounting sense of
excitement.

Fish and other predators gather.

This will be an opportunity for
a feast.

The timing has to be exact.

Each species of coral has its own
particular triggers,

but they must synchronise their
behaviour to ensure their success.

Just half an hour before the big
event,

there is the first
sign of the spawning to come.

Small bundles of sperm
and eggs bulge from the polyps.

When the moment is right,
there is a mass release.

For hundreds of miles all
along the coast, the corals erupt.

Only with daybreak can you see
the true scale of the event.

Great ribbons of coral spawn drift
over the surface of the sea.

After the coral has spawned,

the billions of developing larvae are
swept far and wide

by the tides and the currents.

The vast majority will be
eaten by fish and other creatures,

but the few survivors must then find
a place to settle,

either on a newly-vacated site on an
existing reef

or perhaps to found a new one.

The newest coral recruits
will continue

the work their ancestors began
almost 10,000 years ago.

They are the essential organisms
on which the whole reef depends.

The Great Barrier is what it is

because the tiny coral polyps
never stop building.

And what they have created is one
of the wonders of the natural world.

Next time, we'll cross
the Great Barrier Reef

to meet its extraordinary visitors.

I will meet turtles

that may have travelled
thousands of miles to get here

and the remarkable people

who are trying to save them from
disaster.

I will come face-to-face with
the great predators of the reef.

Wow. There's a huge shark.

They are so beautiful in the water.

And we'll meet a whale that seeks
out human contact,

a behaviour that happens nowhere else
on Earth.

Some come from the open ocean,

others from the land immediately
inshore

and still others from the sky,

to complicate still further
the intricate community

that is known as
the Great Barrier Reef.

For this series,

the production team set themselves an
ambitious challenge.

They wanted me to experience the
Great Barrier Reef as never before.

To achieve that, we teamed up with
a very special research vessel...

..the Alucia.

There aren't many boats like this in
the world and

it's a kind of magic carpet for us.

It allows us to float around the
reef

and for David to tell different
parts of the story.

On board, all the latest technology,

helicopters, a laboratory

and advanced mapping systems.

At the helm of Alucia,

Captain Frank Alika.

The task of getting the ship
into position

for the first big submarine launch
rests on his shoulders.

Some parts are charted less
well than others,

but this particular bit, there's
quite a lot of bombies

and things out there that are likely
to jump up and bite you

on the bottom, and that's
really not what you want.

Fortunately, he's a lot more
hands on

than the skipper was on my first
visit in 1957.

But it was very primitive.

The camera was wound up by clockwork

and it was just me and the chap with
a 16mm camera

and I did the recording.

It may have been a modest shoot but
it was, in its way, ground-breaking.

We worked on locations on the reef

where film crews had never
been before.

60 years later, I'm told we are
poised to make history once again.

This time, to reach new areas of
reef,

I'll have to rely on the Triton
submersible.

And she's very flexible in terms
of how shallow we can come, as well.

She'll work in 1,000 metres happily,

but we can also work in the
splash zone,

so her actual trim system is very
good.

Amazing visibility, as you'll see
when you get in.

Yes, she's a little bit flash.

With just a few short
hours before the first big dive,

the excitement and pressure is
building on deck.

This will be the last
opportunity for the crew

to check the camera gear

and make sure everything is perfectly
in place.

It's been a busy morning already.

We've had soundmen, cameramen

trying to fit all their gear into
the sub.

We're sort of running out of space
for bodies.

There are lots of worries when you
put your 88-year-old presenter

in something like this.

I mean, it's got a very small
area at the top to get into.

There are all sorts of things that
can go wrong.

We're always very cautious.

And even the most limber of sub
operators

will struggle getting in the sub.

David's incredibly active and fit,

but he's 88 and so we were
slightly worried

about how he might get into the sub.

Yeah, that's it, that's the one.

OK, so we're just going to...

See that landing, he'll guide you
right in.

And then you can put your foot
there, David.

Keep coming. Nearly there.
That's it. OK.

You can rest against me if you want.

Nearly sat on the pilot!

That's all right, I'm used to it.
That's what he's there for.

David, as usual, defied
all our thoughts

and just went straight in without
any trouble

as though he was a 25-year-old.

Rest it on your lap. Is that OK?
Yep.

So, that's hatch secure and we are
ready.

The sub weighs almost eight tonnes

and getting it into the water is
a major operation.

There's something quite
extraordinary about the Triton

being launched, standing here
on deck.

Suddenly, the whole back deck area
of the ship comes alive.

You've got people running around.

Everything's incredibly detailed and
carefully planned,

but you're sort of caught in a
whirlwind as ropes fly

and the submarine starts to move
forwards.

You know, this is a very
exciting moment.

You know, this is a big day, even
in the world of David Attenborough.

As we disappear beneath the waves,

out on a support vessel,

underwater cameraman Steve Hudson
prepares to film the sub

as it explores the reef.

So, Nick and I are going to
jump in the water,

descend to a maximum depth of about
30 metres

and shoot exterior shots of the
submarine

as it cruises over the reef.

It can be pretty tiring.

You have to swim in front of it,
swim behind it,

swim beneath it, swim above it,

trying to get a multiple of shots.

But today, because of the strong
currents, visibility is poor.

At first, Steve struggles to locate
the sub through the cloudy water.

Finally, he makes visual contact.

Before we descend deeper and beyond
his reach,

Steve must get his exterior shots of
the sub.

Lead cameraman Paul Williams

captures the action from inside
the vessel.

To get the best footage,

the divers need to coordinate with
the sub team.

It's a task easier said than done.

We're literally in a bubble.

We can't talk to the divers outside.

We had this rather crude
hand signal.

You know, it's like,

"Get out of shot," or, you know,

"Well, just move over that way
a bit."

Can you see his hand signals, yeah?

He's saying, "Thank you."

Thank you and...

We're just going to do the
descent now.

'As the vessel dives deeper,

'we're treated to some spectacular
sights...

Oh, how beautiful.

'..which show why the reef is
one of the most dazzling

'habitats on the planet.'

Oh, look at this lot.

It's jolly nice that someone of my
age

can be taken down in fantastic
comfort.

Grey reef shark there.

No problem about breathing.
No problem about talking.

No problem about your movements.

There's another.

You're just sitting there

and looking at one of the most
extraordinary places on Earth.

A privilege given to very few.