Mediterranean Sea Oceans

They cover two thirds of our planet.

They hold clues to the mysteries of our past.

And they're vital for our future survival.

But the secrets of our oceans have remained largely undiscovered

until now.

I am with a shark.

Yes, yes!

Explorer Paul Rose is leading a team of ocean experts

on a series of underwater science expeditions.

For a year the team has voyaged across the world

to build up a global picture of our seas.

We are doing some pretty uncharted research here.

That is psychedelically purple!

We're here to try and understand the earth's oceans and put them in a human scale.

Our oceans are changing faster than ever.

I've never seen ice like this before!

There's never been a better time to explore the last true wilderness on earth.

Looks good,

perfect!

The team is about to explore the sparkling blue waters of the Mediterranean sea.

The remnant of an ancient ocean,

this temperate sea is now home to over 700 varieties of fish

and almost 10% of the world's marine species.

Surrounded by the continents of Europe, Asia and Africa,

its coastline is one of the most densely populated in the world.

And the human pressure on this sea

is magnified by 100 million visitors each year.

Most people think of the Med

as a holiday destination.

It's hot, sunny,

there's nice sandy beaches,

but it's an ecosystem under pressure.

Western civilisation developed around these shores

but now human activity is threatening to ruin this sea.

The Mediterranean has been critically important for so many thousands of years

but the evidence is there.

The Mediterranean is a shadow

of what it once was.

The team is here to explore the profound effect that man is having

on these endangered waters.

Quite a bit of life here but no large fish.

On this expedition,

environmentalist Philippe Cousteau investigates the delicate balance of marine life here

and tries to protect one of man's most feared predators.

The great white shark is definitely the holy grail, so to speak.

And to search for them here in the Mediterranean, just fantastic!

You actually can't see a way out. It is like you're surrounded on all sides.

Marine biologist and oceanographer Tooni Mahto braves treacherous caves

for evidence of some of the greatest changes to have shaped this sea.

This cave is like a time capsule.

This was once all dry land.

Maritime archaeologist Dr Lucy Blue

explores how the Mediterranean gave rise to one of Europe's first super-powers.

The sea is often seen as that big dangerous expanse of blue

that stops people moving around,

but the Mediterranean is quite the opposite.

It was a super-highway for millennia.

The expedition will begin at the centre of the Mediterranean,

in the waters between Italy and the island of Sicily,

the Straits of Messina.

The team is here to search for a prehistoric creature

that's increasingly threatened.

One of the largest predatory sharks in the world

but one of the most rarely seen,

the six gill shark.

Typically, they're found in about 2,000 metres

or in 6,000 or 7,000 feet of water.

We assume they ride up in the middle of the night to feed,

and then return back to the depths before the day.

To have them here in about 40 metres of depth

where we can get down and see them is super-rare.

There's only a few places in the world where they've been found.

If he's successful,

expedition leader Paul will be one of only a few people ever to encounter this shark.

Filming this vulnerable creature

could give us a chance to learn more about this deep ocean animal

facing threats from fishing, pollution and habitat destruction.

We tend to think that obviously they've been filmed and studied loads

but they haven't, so when I realised a glimpse is a success,

it really puts pressure on tonight's dive.

This rare opportunity

is because of the peculiar underwater geography here.

The Straits of Messina are a bottleneck

connecting two deep sea basins.

Tides and currents create upwellings,

powerful surges of turbulent deep sea water,

that are forced up and through this shallow narrow channel,

dragging up rare creatures normally only found in the depths.

The danger is that with these big overfalls and upwellings,

that I'll get drawn to the surface quickly

and it could be that I could come all the way to the surface

and I can't afford to do that because I'd get decompression sickness.

I'd get the bends.

And it can be serious enough that I can end up, you know, tonight,

I could do that dive, 40 metres, get blown to the surface

and be in a wheelchair the rest of my life.

Adding to the risk,

this dive has to be made at night around the new moon.

There are only a few nights when conditions are right,

with tides strong enough to pull the six gill up from the deep.

At midnight, Paul heads out into the inky waters.

He will head the dive team with Philippe as his stand-by.

I think this is an absolutely incredible opportunity to see a six gill shark

because we know so little about these animals

and the more evidence that we can gather about what they're doing down there, the better,

the better for us to understand them,

and also the better for us to hopefully protect them.

Right Paul's good to go?

Down we go.

Good luck, mate.

We're moving pretty fast actually.

There's a real sense of purpose.

Sharks are crucial to the health of our oceans.

The six gill is almost identical to sharks from 200 million years ago,

a living fossil that offers an insight

into our prehistoric sea life.

There's a lot of activity down here, we're swimming like the blazes.

The night dive reveals some of the sea's nocturnal marine species

like the moray eel.

Paul swims by something that could entice a six gill into the area.

It's not a shark but it's a beautiful octopus.

Octopus, as well as fish and small sharks,

are part of the six gill diet.

But no sign of our shark, I'm afraid.

The rescue boat is tracking the divers' lights,

but diving at night in a strong current is a worry for dive supervisor Richard Bull.

No matter how many times we've checked it,

I'm always thinking, "What haven't we spotted, what is gonna go wrong?"

When things go wrong when you're diving, it's bad.

You know what I think the worst thing is? A missing diver.

Paul still hasn't seen a shark.

He's swimming against an exhausting three knot current

so he is rapidly using up his air supply.

Hang on, we can't see them for a second. Let me, uh...

Suddenly the rescue boat loses sight of the divers forty metres below.

Paul, surface?

Kill all your lights, kill all the lights.

To avoid decompression sickness as they ascend,

Paul and his team need to breathe the pure oxygen the rescue boat is carrying.

If we can't find them, the O2 tanks that they need for decompression,

that are hanging under the boat,

won't be there when they come up, so it's very dangerous.

Mike Kasic is in charge of communications.

Paul, surface?

Paul, surface?

Yes, just reporting, we've started to leave the bottom.

We've lost you, we've lost you. So I need someone with lights

to shine them to the surface so that we can kind of track you, OK?

Roger, Roger.

Keep your lights shining up, Paul.

At last through the gloom, the divers' lights are spotted.

Let's get some oxygen. Oxygen is going in now,

and we're right over the top of them.

We can see the cylinders, thanks guys.

You know your heart skips a beat for a second but we found them.

The relief that the team is safe

is matched by frustration that they failed to find the six gill shark.

What a disappointment.

We have just swum our little legs off.

You know, a bit tired from the exercise

but disappointed really, blimey!

I felt that we would find him, really did.

The next night at midnight Paul dives again.

Right, we're picking up the pace again.

But after another exhausting swim, the dive ends.

No sign of our shark, sorry guys.

The team is beginning to understand

why sightings of this shark are so rare.

I look at the size of the strait

and the small area that we can cover,

although it feels like a whopping great big area,

I realise it's a needle in a haystack job.

Got one chance left tonight.

It's the last night of the new moon

when the tide could bring the six gill shark up from the depths.

So Paul has pushed his equipment to the limit

to give himself as much time as possible underwater.

I've got the biggest cylinders I can carry and swim fast with,

pumped to the absolute max.

This is our opportunity to learn something and help study them

so it means a lot.

Six gills aren't aggressive to humans

so to increase his chances of attracting one,

Paul is attaching a bait bag to his dive belt.

It's not that that great lump of tuna attracts a shark to bite you,

but it grabs a lump of tuna and heads off into the deep dragging you with it,

and that's when you've got to be prepared to get rid of it.

Survival, it's a strong instinct isn't it?

At 1:30 in the morning, the final dive begins.

I do have to tell you, Philippe,

it's absolutely perfect.

We've slowed down a bit because we've come across a John Dory.

It's a fantastic looking fish.

Identifiable by the dark spot on the side of its body,

this fish is another food source for predatory sharks.

But we've got no time to waste, that's for sure.

What are you seeing down there, over?

Communications with Paul have failed.

No I've got nothing, I don't even hear you speaking.

Unaware that Philippe can't hear him,

Paul presses on with his search.

But I can't see anything.

Where's the shark?

Come on, baby.

Where are you?

Paul is down to his last ten minutes of air

when he gets a signal from one of his dive team.

Oh, wow!

Surface, Paul. Surface, Paul.

I am with a six gill shark.

Can you believe this?!

This is one of the largest predatory sharks in the world.

It's a rare encounter with a mainly solitary animal

that spends much of its life at the bottom of the sea,

diving to depths of 2,000 metres.

Look at those eyes. He's got those great green eyes.

The eyes of deepwater sharks like the six gill can reflect light,

enhancing their vision

and allowing them to see in the gloom of the deep sea.

1, 2, 3, 4, 5, 6...

yeah, there you go!

Most sharks have evolved to have just five pairs of gills

but the six gills on this shark

make it similar to sharks dating from 200 million years ago.

It's like swimming with a living dinosaur.

The sixth gill is thought to help them breathe

in the oxygen-depleted waters of the extreme depths.

That's not the only primitive feature.

Its teeth and the structure of the jaw

mean it closely resembles fossils of sharks from the Jurassic period.

Six gill sharks spend most of their life at extreme depths

where they can't be reached,

so rare film like this will help scientists to study them.

Ah blimey, there he goes.

Philippe still doesn't know what's happened

but as the divers begin to ascend, contact is restored.

OK Paul, surface. What did you see down there? Over.

We're now, uh...

slowly coming up to our first stop,

but we've all got big grins!

Paul, surface, uh...

Confirm, did you see a shark?

Did you see a six gill, over?

Roger, Roger. Saw a six gill shark!

And he was a beauty!

And it was a wonderful experience,

we were in contact for five or ten minutes.

Five or ten minutes?!

Of course, the five or ten minutes the comms were out!

I began to wonder if we'd see him before we ran out of air.

-That's brilliant!

-Guys, it was worth the effort,

totally worth the effort.

That is fantastic!

Paul, my man, how was it?

You'll never believe it.

We just swam down and just when we were thinking,

burning up too much air trying to find this,

and then he just came straight in.

Just as smooth and as easy as you like!

Sharks play a crucial role as predators in our seas and oceans,

weeding out the sick and injured,

but numbers are decreasing rapidly.

Later in the expedition, the team will investigate

how another shark could be at risk in this fast-changing sea.

The Mediterranean is famous for its clear blue water,

but that could be a sign of its vulnerability.

Clear water indicates low levels of plankton,

a crucial source of food in the sea.

So Paul and oceanographer Tooni are using a secchi disc,

a standard oceanographic tool, to measure the clarity of the water.

-OK, ready?

-Yeah.

In nutrient-rich waters the disc would disappear within a few metres.

There we go.

So there's nine.

-Still seeing it?

-Yeah, totally.

Eleven.

That's the end of it, we can't go any deeper!

-It's as clear now as it was at one metre.

-That's amazing.

The clearer the water, the less plankton there is.

That means we're in very low nutrient conditions.

That is essentially why the Mediterranean is so blue.

There's no microscopic plant or animal activity

which means there's nothing to suck the light out of the water column.

The Mediterranean has some of the lowest nutrient levels of any sea.

This restricts how much can live here,

as there's a limited amount of food,

making it a delicate ecosystem

particularly vulnerable to human activity.

To find out just what marine life the Med is capable of supporting,

the team's heading twenty-five miles south-west of Sicily,

to one place that should be full of life -

an enormous underwater volcano.

It's 8:30 and we're on site.

We've travelled all night and woke up this morning

to see that we were in position and we've found the summit of the volcano

which is right under the boat right now.

Ferdinandea is over four hundred metres high

and has a base that measures 750 square kilometres.

Its tip is just eight metres from the surface.

Many volcanoes were created

as a result of the Mediterranean's tectonic plates colliding during its formation.

Some breached the surface to form islands,

which is exactly what happened to Ferdinandea in the 19th century

as this contemporary painting depicts.

It turns out when it was up, in 1831, it was actually a proper island.

It was 60 metres high and something like four kilometres circumference,

just under three miles round.

But it turns out that it only lasted six months, just magma,

and it just all quickly turned to ash

and a few big seas and rain and general weather,

and it demolished the top and once it got low,

the sea knocked it back.

Ferdinandea is now completely underwater once again,

one of thousands of seamounts around the world

which are magnets for marine life.

So the team goes to find out what's living here.

This volcano was created at the collision point

of the African and European plates.

Check out the ridges.

It's very strange how there's a rippling effect

in the black volcanic basalt.

The ridges are caused by the speed of the water current

that passes over them.

This fertile volcanic sand

allows the millions of microscopic plant and animal larvae that float in the open sea, to grow here.

Seamounts are biodiversity hotspots

because they provide organisms with a place to land and settle

in an otherwise featureless flat ocean.

As deep water hits these underwater mountains,

it rises, bringing nutrients from the seabed,

creating a rich feeding ground.

These places, they've become like an oasis

because they've got such deep waters all around us

and this thing coming right up in this beautiful light zone

attracts an abundance of life.

Marine life uses seamounts as habitats, as spawning grounds,

even as stepping stones while it travels around the sea.

Lucy and environmentalist Philippe

should find the summit teeming with life.

There are lots of small schooling fish which is a good sign.

Oh, and a sea urchin!

Sea urchins just love all the algae that grows in here.

But it soon becomes apparent something crucial is missing.

Quite a bit of life here but no large fish.

There's no sign of the open water fish

like sardines, tuna and grouper that should be here.

This is essentially an artificial reef in a big void space

so all the little fish come here because they've got places to hide.

And the little fish then attract the big fish

but it also attracts the fishermen,

so I'm not surprised to see not a lot of big fish here in this area

because most likely the fishermen come here frequently.

Fishing has been an integral part of Mediterranean culture

for thousands of years.

Until recently, it was a largely sustainable industry.

However, since 1970 fishing in the Med has increased by almost 50%.

Conservationists now warn the entire sea is endangered.

The problem with the Med is because technology has advanced so swiftly

in the past 50 or 60 years,

and because it's such an enclosed area,

this is the place where the technological advances are going to have the most impact.

That impact is particularly felt

by an iconic species of the Mediterranean -

the Atlantic blue fin tuna.

They're pretty incredible animals.

They're fast, one of the few fish that are warm-blooded,

they're very complex, very interesting animals,

they're ocean-roaming all over the world,

and they're very highly prized.

The value of the estimated total blue fin tuna catch in the Med

is around £400 million.

This has triggered the rise in industrial fishing.

Philippe and marine biologist Tooni are heading off to investigate

one of the more recent developments in the harvesting of this sea -

a tuna farm.

It almost looks like a kind of rubberised pen

you'd see at an amusement park for people to go splash around in.

This is going to be full of tuna.

And ironically enough,

this is pretty much the only place I'm going to see such large schools.

-Any more.

-Any more.

There are now over 40 offshore tuna farms in the Mediterranean.

One, go for it.

Go for it.

Just look at the size of the net, it's huge.

In one way I was really looking forward to seeing these tuna because

I've never gotten to see them before in the wild.

-But seeing them swimming in circle after circle, over and over...

-Yeah.

20,000 to 30,000 tons are caught each summer in vast drag nets,

and towed to the tuna farms.

Well, these tuna have just recently been caught.

They'll be fed regularly to fatten them up

and then once they've reached a certain size,

about 200 to 300 kilograms,

they'll be taken to the mainland where they'll be shipped to Japan.

These wild blue fin tuna migrated here from the Atlantic Ocean

to spawn in the warmer waters.

They swim with their mouths open to force water over their gills.

If they stop, they suffocate.

Look at that blue stripe.

That's what gives them their name blue fin tuna.

It's a beautiful blue colour.

This farm operates within the law

but conservationists believe the high value of this tuna

means some fishermen are exceeding quota limits.

What's more, some are even flouting restrictions

on the size of the tuna they catch.

The fear is that more and more tuna farms are catching juveniles.

Yeah, this is depleting the population

before they even have a chance to procreate

and start the next generation.

And that's pushing the blue fin population here to the brink of extinction.

Scientists believe that as much as 20,000 tons of blue fin tuna

are caught illegally in the Mediterranean every year.

The Med's most iconic fish,

and the traditional fisheries it once supported,

are now close to collapse.

It doesn't just have an implication for the Mediterranean.

It has an implication for the Atlantic

because they're a migratory species.

For the survival of the Mediterranean economy

and survival of Mediterranean traditions

that have been in place for thousands of years,

you have to maintain a population of that species

and that isn't happening.

The exploitation of this sea is no new phenomenon.

Man's influence has been felt here for millennia.

Some of the greatest civilisations in our history

have used the Mediterranean to their advantage.

Maritime archaeologist Dr Lucy Blue

has worked in the Med for much of her career,

exploring how this sea is uniquely important

in the development of western civilisation.

You know this is where cultures developed, around these shores.

The sea, in this instance more than anywhere else in the world,

facilitated the communications and the development

of these civilisations.

The Romans ruled this sea over 2,000 years ago

and became one of humanity's first superpowers.

Lucy has brought the team to the Egadi Islands to the west of Sicily.

She wants to search the wreck of a Roman cargo ship

for any clues to what was being traded,

and how far these routes stretched across the Mediterranean.

It's 1st century BC so it's the early part of the Roman period

where they've just taken Sicily over

so it's about development and expansion.

They're going to dive to just one of hundreds Roman wrecks

that have been discovered in the Med,

clear evidence of the scale of traffic

around this sea in ancient times.

OK, so we're gonna moor up to the buoy that you can see over there

-where the other boat is.

-Yeah.

And there's a shotline there. It goes down to 12 metres

and basically that just slips down quite gradually

to about 24 metres.

Is that good? You're clear. Clear behind.

On your mark, clear.

The wooden structure of the shipwreck

has long since disintegrated.

What remains is some of the cargo it carried,

a mound of amphorae, enormous ceramic containers.

Just getting a first glimpse of the amphorae on the sea bed

and it's really quite remarkable,

and although I have worked on a number of shipwrecks over the years,

I have never actually seen such a large number of amphorae

concentrated in one spot.

The wreck dates from around the 1st century BC.

That's over 2,000 years old.

Now that's a fairly intact one, there.

But what were the Romans trading?

Shall I grab that end?

What have you got?

I've got 120.

It's huge.

From the shapes and the fact that they were lined with bitumen or pitch,

they likely carried wine.

Probably would have carried about 20, 25 litres of wine.

You can see the shape of them.

It's perfectly made to slot into the hull of a vessel.

This is how they would have stored them,

sort of one on top of the other in the hull of a Roman merchantman.

Having found out that these amphorae are likely to have carried wine,

Lucy now needs to look for any clues that might reveal who produced it.

There's one that has the names of the family that produced the wine.

"Papia".

Based in southern Italy,

the Papia family were a powerful dynasty of winemakers

who exported it around the Mediterranean.

It's likely that they were transporting them from Sicily

maybe even to north Africa.

This would have been part of the general trade in wine and olive oil,

garum - which is a fish paste -

that was being conducted around the Mediterranean at this time.

This is a record of a trade that linked two continents,

and the scale of this operation

shows how effectively the Romans established trading routes

around the Mediterranean.

There are about forty amphorae here,

but these are only a fraction of the original cargo.

There used to be about 400 to 500

but these have been taken by looters.

It's a big problem in the Mediterranean.

Treasure hunters have damaged and stolen

many of the rich but fragile historical remains

that scatter the floor of the Med.

To protect what remains of these amphorae,

this underwater archaeological site

is being monitored 24 hours a day by CCTV.

The pictures are fed to the nearby island of Favignana

where they're monitored by police.

Buon giorno, possiamo guardare?

-Prego.

-Grazie.

-What was that?

Just asked permission, want to have a little respect.

-Ooh!

-We've got some visitors.

There's Paul right in front of the camera. And there's Lucy.

I think this whole project is so unique,

the fact that they're very interested in the conservation of these relics.

It's kind of sad that they had to in the first place

but it's very cool that they do it.

Since CCTV was installed,

not a single Roman amphora has been stolen.

The cameras protect what remains of this valuable site,

a record of how the Mediterranean sea enabled civilisations to expand.

For the team's next mission,

Paul and Tooni are heading off to Mallorca

to look much further back in time.

They'll be diving underground to search for evidence of huge changes

which transformed the whole Mediterranean,

changes that helped bring people here in the first place.

Mallorca lies in the western Mediterranean.

Beneath the island's east coast is a vast network of flooded caves.

This cave system is connected to the sea

but Paul and Tooni must drive several kilometres inland

to reach the entrance.

In these flooded caves are unusual formations that you can only see,

apparently you can pick them up in the Bahamas and a few other spots

but this is a really rare opportunity to learn more about the Med.

It's probably the most dangerous diving we're gonna do on this!

Yeah, that's going to make me feel better. Thanks mate(!)

-Here we go.

-That looks like a cave.

Doesn't fill me with joy, it has to be said.

It doesn't look very inviting.

Paul and oceanographer Tooni will be searching for proof

of when Mediterranean sea levels dropped many thousands of years ago,

changing the coastline and creating the ideal conditions

for people to spread and settle.

They'll have to brave a perilous section of flooded caves

and though they're both trained cave divers, this is a dangerous task.

There's a definite sense within me that this is a risky dive.

As soon as you can't get to the surface,

there's a lot of opportunities for things to go wrong.

They are hoping to examine rare rock formations deep inside the earth.

The dive begins with a claustrophobic entrance way.

Here we go. The trick here, Tooni, is going to be head first for sure.

Just have to take our time as we go through this squeeze.

The visibility has gone to next to nothing.

Very, very, very tight indeed, this.

You couldn't possibly go through much smaller of a space.

One hand at a time, one hand at a time.

It goes down as well.

Tooni and Paul dive further and further down below ground

into the cave system.

Kind of a brutal start this, no visibility and very cold.

As they travel deeper into the network,

they reach a mysterious water haze.

Here we go, halocline coming up, Tooni, look.

This haze, or halocline, is caused by light rays diffracting

as they pass through the different densities of clearer fresh water,

and denser salt water.

It's the first sign these inland caves are connected to the sea.

I love the fact that you've got fresh water above

and sea water below,

and then you get this crazy kind of lime cordial effect

where the two meet.

I've never been able to SEE density before.

Physics in action.

Coming out of that halocline, look how clear it is now.

Oh, that is beautiful!

The divers emerge into the crystal clear water of an enormous cavern.

Wow, Tooni, look at the size of this room.

This is just incredible!

I'd always fancied being an astronaut

but maybe this is as close as I'm ever gonna get.

Instead of outer space,

it's like the cave divers use that word, "inner space",

and it's very true.

Deep inside the earth, they've found what they've been looking for,

spectacular sculptural rock formations,

that shouldn't even be here.

We've come underwater here, below sea level,

and yet we're seeing these stalagmites on the bottom

and the stalactites from the ceiling

which means that this cave was once dry

because those things only form in dry caves.

These majestic structures have formed over time

by mineral-rich water dripping into dry caves.

To find them in this flooded cave

is proof that the sea level was once much lower than it is today.

These rare bulbous formations around the stalactites and stalagmites,

found almost nowhere else on earth,

can reveal when the sea level changed.

This bulge was formed when the sea level was here.

Lapping water deposited minerals

which created this blancmange-like structure.

By dating these mineral deposits,

scientists can build up a chronological record

of changing sea levels in the Med.

Sea levels have been going up and down

over hundreds of thousands of years.

This evidence proves that 60,000 to 80,000 years ago,

the Mediterranean sea was shallower.

Lower sea levels exposed new ground

and created land bridges between islands.

This allowed early humans who'd migrated out of Africa

to move around the Mediterranean, settling on its coasts and islands.

This cave is like a time capsule.

It proves how much the Med has changed

and that's had a huge influence.

The Mediterranean has been host to humanity

for hundreds of thousands of years.

Today over 150 million people live around its shores.

That number almost doubles in the summer

with the influx of holidaymakers.

Pollution, fishing and coastal development

are putting enormous stress on these fragile waters,

threatening marine life.

Rare species are most likely to suffer.

And one of the Med's most endangered

is so elusive many are surprised to learn it's here at all.

Philippe wants to investigate

why the Mediterranean is home to one of our most feared predators,

the great white shark.

People think oh, Jaws,

sharks are these monsters of the ocean coming to eat us,

but sharks are critical to the health of the marine environment

because they're apex predators.

They have a perfect place in their ecosystem,

balancing and keeping it healthy.

They are...beautiful.

These great whites were filmed off South Africa.

They're most likely to be found there,

or off California and Australia.

The clear waters of the Med might seem an unlikely habitat for this predatory shark

because of the limited food supply.

But there have been rare sightings

to suggest the great white is living here.

This extraordinary footage was recorded ten years ago

by a fisherman on holiday in the Med with his son.

It shows a great white shark circling the fisherman's boat

before tearing chunks from a small fresher shark he'd caught.

But sightings like this are extremely uncommon.

There is some video of great whites in the past

but any evidence that we can gather

to prove that great white sharks live in the Mediterranean

would help us to protect these incredible creatures.

To investigate why great whites could be here,

the team is heading to the middle of the Sicilian channel,

to the tiny island of Lampedusa.

This must be him, he's headed right for us.

That is my man! All right, finally!

-Buon giorno!

-Good morning!

-How are you, man?

-OK, great!

They'll be working with patron of the Shark Trust

and world expert on great whites in the Med, Ian Ferguson.

We're ready for you.

Ian's been looking for the great white here for over fifteen years

and he's convinced there's a pattern to the occasional sightings.

Have the sharks that have been caught

in this particular month in this area just been pure one-offs,

or are they actually here for a reason?

And my longstanding hypothesis

is that the animals are here,

and the reason is to give birth.

The Sicilian channel is the only location

in the entire eastern Atlantic region

where both pregnant and new-born great whites have been sighted.

Yeah, we think it's about three...

Ian believes this could be one of only a few nursery areas

identified anywhere for these endangered sharks.

It's an area of great importance,

it's obviously a very important habitat for them

and we need to get to understand why is this area so important

and what can we do to protect the sharks.

So what might make this a suitable breeding ground?

The harbour is right there. The proposal is to come round here,

a deep dive there on the wall - you know, 40 metres -

to check out the habitat, really.

The idea behind this is that this could be potential for feeding,

-this is what great whites like to eat.

-Sure.

Tooni and Lucy dive to look for any evidence

that this might be a great white nursery.

Now keep your eyes peeled out there for large pelagics.

If we're going to see them anywhere, we should be seeing them here.

Compared to other parts of the Med,

the warm water of the Sicilian channel is rich in nutrients.

This should attract pelagic or open water fish,

as well as dolphins and turtles that great whites feed on.

Lucy, there's a shoal of damsel fish just here.

They're very, very territorial fish,

so this seems to be quite a productive area we're in.

Oh, that's a big grouper!

Bottom-dwelling fish like this

are a typical part of the diet of juvenile great whites.

Because this is such a great place for fish,

it's also a great place for sharks.

And there's further evidence to support Ian's theory.

This shallow shelf is typical of the habitat young great whites need.

It keeps away predators like blue and mako sharks

that don't hunt in shallow waters.

But at the surface, events take a turn for the worse.

I've just been to see the captain. There's gales forecast.

It'll be 25 knots-plus, which is...

you know, at sea, isn't the worst weather,

but for what we've got in mind, it's never going to work.

With the wind picking up,

it's urgent to get Tooni and Lucy back on board.

All divers, all divers, surface.

We need to get out of the water as soon as possible.

The wind's really picking up now, the wind's really picking up now.

So we've called Tooni and Lucy back early.

We've got the main engines running now.

We're going to get the guys in, and run for Lampedusa, fast.

The storm's an unwelcome delay to their investigation of the great white in the Med.

-It's a totally different sea out there, isn't it?

-Yeah.

It's like the North Sea and it's getting rougher by the minute.

Next day, the storm has subsided...

Keep pulling on yours, Philippe.

..and the team decide on a last, hugely ambitious attempt to gather direct evidence,

laying a bait trail of chum -

pulped oily fish - to try and attract a great white to the boat.

We're going to deploy the most fantastic shark cage on the planet,

get some people in there, chum and chum and chum.

See if we can find some great whites.

Everyone's aware it's a long shot.

They now only have a few days

to create a chum slick big and nasty enough to attract a great white.

-You got it?

-Yeah, bung it, bung it.

Give it a shake to start it off.

Bung it.

-Just revolting.

-It's horrible, isn't it?

Overnight, the fish obviously starts to deteriorate,

so I'm trying to just get the fish mashed up.

It'll be a very strong mix

and what we're trying to achieve is a very strong odour trail,

like a corridor for the sharks to follow right up to the boat.

That smell is totally revolting.

Great white sharks have a highly developed sense of smell.

With tiny holes in their snout, it's thought they can detect

minute drops of blood in water from up to three miles away.

-I'm going in.

-That's it. Speed is everything.

Although they have the reputation for being man-eaters,

great whites rarely attack humans,

but Philippe can take no chances

and uses the cage to keep shark watch underwater.

Man, it's rough down here!

If we get a hint of seeing a great white shark in the Med,

doesn't matter how uncomfortable we are.

Long day, long night.

We've just got to keep going

and we're doing everything we can to keep our chances high.

The whole team is going to be on watch

and we're just going to keep at it, all hands, 24 hours.

The team keeps chumming through the night

and the oily fish slick attracts a tantalising abundance

of sea life towards the boat.

It's just gone midnight and the chum slick is suddenly coming alive.

Here comes...

What's that, a flying fish?

These fish have long fins on their sides

which they use to fly above the water for around 50 metres

to escape from predators.

As well as flying fish, there are needle fish and a pelagic octopus.

Fantastic. Slick's working, then.

The conditions are right

and the smelly chum slick is buzzing with life.

Great whites often hunt at night, using their sense of smell

to locate their prey, so Philippe returns to the cage.

All right!

It is a little choppy,

but still good conditions and I'm not giving up hope.

The last sighting of a great white shark,

that we know of, in the Mediterranean,

occurred right around here about a year ago.

What's even more exciting is that the great white sighted

was a juvenile - only about five feet long -

which makes it a critical place for the great white shark.

So even the slightest sign of great white activity here

could be significant.

-We'll see, man. We've got all night, see what happens.

-Just keep going.

Yeah, it's all we can do.

With only a few hours left of the expedition, Ian is on dawn watch.

Then, as morning breaks...

Guys, we've got a chum bag pulled out.

One of our mesh bags, the red one, has been pulled out.

-That's great news, right?

-It takes a lot to do that.

-That's good news, that. Something's happening.

-Yeah.

So we have definitely had a shark respond to our chum?

It certainly wasn't those fish!

It's happening! Can you believe it?

Encouraged by the encounter,

the team tries everything to lure the shark back.

But as the expedition ends, the bite is the closest they get

to finding evidence of this endangered creature.

That's it!

It's a tantalising end to the trip.

Down a bit, mate.

But perhaps not such bad news for the shark.

Although it's a slightly sort of perverse way of looking at it,

one side of me is somewhat relieved that

the animals still remain so cryptic and so distant from us

that we're finding it, with all of our effort,

difficult to actually get them to come to us,

which is a shame for us, but possibly good news for white sharks.

We've only ever explored maybe 5% of our oceans,

and in a sense, I think that not finding the great white

is an extension of that mystery.

As the team have seen,

humankind is encroaching more and more on this sea.

The great white might not be able to avoid us for much longer.

During this expedition,

the Mediterranean has revealed some of its many secrets.

Oh, wow, can you believe this?!

The team has uncovered proof of this sea's dramatic past

and explored the long relationship

humans have had with the Mediterranean.

The expedition has also shown how humans

can put untold pressure on a delicate ecosystem.

Quite a bit of life here, but no large fish.

I'm not comfortable with always using the word "fragile"

around the earth because I don't think it's a fragile planet.

I actually think it's very, very robust,

but the Mediterranean sea - because it's surrounded by so much input

and there's so much stock being taken

and we're asking so much of this small sea -

that I think anybody that came and experienced what I just have,

I think it would totally reset people's thinking and attitudes

towards the Mediterranean sea.

This sea is many things to many people -

a holiday destination,

a historical treasure chest, a food resource for millions.

It's a rich and diverse environment

with a precious history and a vital future, both of which need securing.

Next time,

the team braves one of the most hostile environments on the planet -

the Arctic Ocean.

They dive beneath the vanishing ice cap

and explore how changes to this frozen sea

are threatening the ocean's life, and the rest of the planet.

We are completely dependent on the stuff that keeps the planet cold.

Subtitles by Red Bee Media Ltd

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