Indian Ocean 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.

I am with a six-gill 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.

We're about to see one of the most remarkable creatures in the Indian Ocean.

And this is the only way we can get there.

This is a dive of a lifetime. It's not going to be very easy.

This expedition will explore the third largest body of water on Earth, the Indian Ocean.

More than 6,000 miles wide, it covers 13% of the world's surface.

It's home to 5,000 species of fish, many unique to this sea.

But it's an ocean on the edge.

Global pressures like climate change and overfishing threaten to push it to a tipping point.

The team has come to the western Indian Ocean to find out what effect these changes are having.

Environmentalist Philippe Cousteau is the grandson of ocean pioneer Jacques Cousteau.

He'll investigate the threat to one of these waters' greatest predators.

By removing them in such large numbers, that has drastic impacts on all the other species underneath it.

Maritime archaeologist Dr Lucy Blue will experience the treacherous

effects of the unpredictable currents here.

She hit this reef behind us and then broke her back.

And marine biologist and oceanographer Tooni Mahto

will explore what can be done to save this pristine wilderness.

What we're looking at here is almost the Indian Ocean equivalent of a garden centre.

The expedition begins off the southern coast of Mozambique.

Paul and Tooni have come here in search of the largest population of manta rays in the world.

We actually stand a chance here of being right alongside

or underneath or right with these huge mantas.

-Some of them are about five or six metres.

-Eight metres.

I'm going for a giant eight-metre one.

Eight metres across - that's a huge fish!

It's very exciting indeed.

The team's been brought here by a mystery.

76% of the manta rays here have been attacked by sharks, attacks that

should have decimated their numbers.

So, how have they survived?

Ready, ready, ready.

It's a beautiful sight.

The visibility is a little bit murky.

It means there's a chance this water is very plankton-rich.

Here, close to the edge of the continental shelf,

the plankton is fed by nutrient-rich water welling up from the deep.

It helps support an entire eco-system, everything from giant potato groupers...

..to poisonous lionfish.

Tooni spots a sign that they're in the right place to find mantas.

This is a very particular environment, a cleaning station.

The clue?

These tiny fish.

There's a whole load of small cleaner wrasse that

are waiting here, the very small black-and-white-striped fish.

And they're waiting here until the mantas actually come here, so they can go up to their skin

and pick off all the parasites, which apparently feels really good on the mantas as well.

They seem to like the sensation.

So it's a bit like going for hair and make-up and a massage at the same time.

Looking for mantas.

I'm waiting for one to just sneak up on us from behind!

I keep imagining that I'm seeing them coming out of the gloom.

Tooni, there's a manta. Come on!

Oh, oh, oh! Oh, my goodness!

Oh, my goodness!

It's a whopper, Tooni!

That is beautiful!

Oh, my! So elegant.

The largest of the ocean's rays, mantas weigh up to one and a half tonnes.

Yet they fly gracefully through the water, using their wing-like fins.

They are bizarre-looking.

The horns at the front that gave them their name, the devil ray.

The horns can unroll to funnel food into the manta's mouth.

As the water passes through, spongy tissue traps the plankton they feed on.

But this one shows no sign of a shark bite,

so it provides no clue as to how so many mantas survive these attacks.

And time has run out.

We're both low on air, both got 50 bar, so we need to leave the bottom.

Unfortunately, in man versus manta, the manta gets to win this one.

There was a whopper behind Tooni!

And then we didn't see any more.

They have located a manta cleaning station, but they still haven't found what they're looking for.

The manta that we did see didn't have any injuries at all.

And it's actually specifically the injuries that I'm really interested in going and having a look at.

With the light fading, they decide to try again in the morning.

Next day, weather and sea conditions are perfect.

But Tooni's not.

Oh, God!

SHE RETCHES

I'm feeling really ropey, and I think I've got a stomach bug or something.

Being sick underwater could be deadly.

With the masks we're using, which are full-face masks,

where the air comes from is right down in the front.

And if someone was to throw up in them,

there's a reflex inhalation, isn't there, when you breathe in?

That reflex inhalation, which can't be controlled, would bring stuff back into the throat.

There's a chance of being brought to the surface unconscious.

She's experienced enough to know

that she can't just push it.

I think you should probably go, and I'll sit this one out.

I know we saw the mantas yesterday, but we didn't

see specifically what it was we came to see.

I've read about this for years.

I would be really interested

to see the mantas and the cleaning behaviour.

It's just frustrating, really frustrating.

It's all up to Paul to find out what helps the injured mantas survive.

This time, the elusive mantas turn up straightaway.

Look at this!

Look at him go!

Effortless, but incredibly fast.

What's really fascinating is that the whole life on this reef changes when the mantas come and go.

All the attention is focused on them.

There's a shark bite right there at the very back.

A shark attack like this is often fatal.

Oh, there's another one. This one has two great bites out of the back end.

No-one's sure why so many of these mantas have been attacked by sharks.

But the location of their wounds is less of a mystery.

The manta's eyes are on the side of its head, leaving a blind spot

directly behind, exactly where the sharks have taken a bite.

I'm gonna stay still here

to see if he'll come my way.

Here he comes.

Just look how big he is compared to me!

And look just how well he moves.

And here's some cleaning. Can you see the cleaning going on?

That's what I'd dreamed we would see.

The yellow butterfly fish and moon wrasse clean the wounds, removing dead and infected tissue.

It's like pulling into a hospital and having your wounds dressed.

Stops infections forming.

More and more mantas arrive to have their wounds treated.

This could be why they're so resilient to shark attacks.

A cleaning station with fish that target the shark wounds.

Behaviour that's rarely seen.

Really, really marvellous.

Then here comes this great manta. Just kind of came over me. Shark wounds on the back end,

and was smothered in cleaner fish. It was a great dive.

The cleaning station is a perfect example

of how complex interactions make the world's marine eco-systems function.

Every living thing here is vital to this ocean's health, right up to its most extreme predators, sharks.

Next, the team will investigate what's happening to shark populations in this ocean,

because sharks have turned from the hunters into the hunted.

Up until now they have reigned supreme, and we are totally decimating their numbers.

And, as the apex predator, by removing them in such large numbers out of these areas,

that has drastic impacts on all the other species underneath it.

Overfishing means shark numbers are plummeting.

Estimates suggest that each year as many as 73 million sharks are fished worldwide.

26 shark species are now listed as critically endangered.

Along this coast, shark fishing has grown dramatically over the past few years.

Philippe and Lucy have come onland to find out more.

This is Pomene in Mozambique.

Lucy and I are here to try and figure out kind of exactly what's happening and why and how.

We're here early because this is when they take their boats out to check their lines.

Little is known about shark fishing in this part of the world.

It's a unique chance to investigate it first hand.

How many sharks does he catch?

HE SPEAKS IN LOCAL LANGUAGE

Between three and seven.

-Wow. So is he from here?

-He's from Vilanculos.

-Oh, he's from Vilanculos. And he came here five years ago to fish?

-Yeah.

But Vilanculos is several hours away.

These fishermen are not from here, and the locals have no history of shark fishing.

This is something new.

These people have come or been brought here deliberately, within

some structured organisation, to specifically do this type of fishing.

And that is most unusual.

The fishermen head out to check their three kilometres of line with its 65 separate hooks.

This one boat can land up to 1,000 sharks in a single year.

The fishermen return with their catch.

Two males.

Little blacktip reef shark.

Both sharks are extremely young.

These aren't anywhere near sexual maturity.

They're little baby reef sharks, maybe two years old, a year old maybe.

Sharks don't start reproducing until they're several years old.

When they do, most have few offspring.

So catching young sharks like these is particularly worrying.

The worst thing for me is the fact they're so small, you know.

They haven't reached maturity.

So there's no reproduction. That's the end of this particular lineage.

But why is this industry growing so fast?

The fins are the most valued part of the catch,

the essential ingredient in the Chinese delicacy shark-fin soup,

demand for which is growing rapidly.

It's pretty barbaric when you see it here now.

-It's

-BLEEP.

-Look at this.

This little pile of fins for...

..soup.

The waste is disgusting.

The only reason they sell the meat is because they can get a few cents for it.

It's worth nothing.

The only reason they're doing this is for those fins.

And there's a huge incentive.

How much will they sell those fins for?

The fish, big one, bigger than the fish today,

only the fins, they can make 50, 60.

50, 60, just the fin?

In a country where most people live on less than 1 a day, six sharks can provide a year's income.

There you go. Merry Christmas.

The fishermen show off a recent catch.

This pile of fins is worth a small fortune.

-Where do they go now?

-They go to Maputo,

and then they go out.

According to the fishermen, the big money means that regulations

to control the export of fins are being ignored.

So the trade flourishes.

Across the globe each year, millions of sharks continue to be wiped out.

It's scary when you think that so few individuals can come into a community like this

and take out so many animals.

Over 1,000 animals a year come out of this little cove!

-This is not big!

-Four boats.

-It's shocking.

-And when you think what's going on around the other shores of the Indian Ocean...

And, to add insult to injury, shark fin has no flavour.

They have to flavour the soup with chicken broth, for God's sakes.

It's ridiculous.

It's absolutely ridiculous.

They've discovered that along this coast shark fishing is an organised industry driven by fat profits.

It's just one part of a global trade that's decimating species

and disrupting the balance of life throughout the Indian ocean.

But overfishing is not the only threat.

A changing climate will impact the ocean, altering its weather patterns.

These are dominated by heat transfer to and from the sea.

But this is a complex process we know little about.

To try and find out more, the expedition will take part in a huge project

run by scientists around the world, including the British Met Office.

They head north to the equator, where the heating effects of the sun

have a powerful impact on the ocean and on the weather.

There's no clearer example of the link between the oceans and the climate than a tropical storm.

The energy in the Indian Ocean!

There it is, coming right at us!

Maybe a bit more than we ideally want right now.

-I don't know.

-It's definitely coming. It's a proper good

pile of rain, and the sea's picking up a little bit.

The heavens have opened. It's bucketing down.

The captain advises that this thing rolls quite a bit.

It's not unusual to have two feet of water swilling around on this deck.

Storms are powered by the constant exchange of heat and moisture

between the ocean and the atmosphere.

So, understanding these processes is vital.

I've got goosebumps!

Look at the sea. Look what the rain does to the sea.

It's knocked down. It's fantastic.

The global project to gather data on the forces driving our weather

is based around one vital piece of equipment.

I've gotta make sure that it's in there.

I can see it's been opened by customs.

You never know with these things. It's supposed to be yellow and expensive-looking.

This is the Argo float, a robotic buoy, designed to gather

readings on temperature and salinity from the depths of the ocean.

How this thing works is it descends to 1,000 metres and then comes back up again.

Uploads all of its data and then sinks again.

This will be one of a vast network of floats transmitting their data

to satellites to build up a dynamic picture of the ocean.

The plan is to launch it into an area that's poorly covered by

Argo floats to help plug a gap in the survey network.

I should hear at some point...

ARGO FLOAT BEEPS

There we go, one. That's working.

Now it's turned on, it's programmed to be deployed in just six hours.

Here we go!

I can hear it. It runs for five or ten seconds and then stops.

You can't put enthusiasm into this unless

you have some empathy and some interest in it, and I do.

I really do. I mean, this is a... Hang on.

Yeah, there it goes again!

En route to the launch site, the £6,000 worth of equipment

must be kept upright while it makes contact with the satellite network.

What sort of information is being collected in this?

It's temperature, salinity and depth.

And when it comes up, it's also position as well.

The data will help scientists worldwide

to improve climate-change prediction and tropical-storm forecasting.

So how much longer do we have before it needs to be in the water?

It's six hours from when we turn it on. It's now 10,

so four hours, 50 minutes.

But the journey is taking longer than expected.

It would suit us better if we could be on the eastern side of the target area, where it's deeper.

A bit twitchy about... Everything seems to happen just once.

The plan is for Paul to be in the water when the float is launched to make sure it deploys correctly.

All systems go, and we've got 45 minutes to go.

It took a little bit longer to get here than we thought.

As you can see, I'm not dressed for the dive yet!

But we just can't afford to be loafing at the moment.

Far from land, with no reference points to gauge position and depth,

dive safety supervisor Richard Bull is concerned about Paul's dive into the big blue.

What I'm worried about is sinking down without noticing it.

Because you get to a point where

you're so deep, you can't see the surface,

you can't see the bottom, you can't see that way and you can't see that way.

You can't tell which is up and which is down.

Yeah. It'd be easy to do on this dive, because I'm just watching that yellow float.

We're getting late, we're going to miss it.

The float is timed to begin its first descent in just a few minutes.

Lucy is in charge of the crane.

You know yourself, when handling a crane...

"You know yourself, when handling a crane"!

I have to point out, this is the first time I've done any crane-handling!

I'm really, really concerned

about it hitting the side of the boat, though.

Wahey! Oh, God!

A tiny bump against the metal hull could dent the casing, creating a weak spot that might

rupture deep below the surface, where the water pressure will reach 200 times atmospheric pressure.

Five minutes, five minutes.

The rolling of the boat is also a problem for Paul.

I'm just swimming out of the way here because our dive boat is right there.

I don't want to bang myself into it, and he's going to have to start positioning soon.

And that propeller's going to start going round, so I want to get it out the way.

Woo!

I have to make a note of a number of things so the Met Office have an

understanding of the sort of basic sea state when the Argo's launched.

Knocks and bangs against the side of the vessel? Apart from the initial swing I induced, I think it was fine!

God, I'm shaking a bit, actually, because I don't want to mess it up. You've only got one go.

You can't take two on this one!

But the descent time comes...

It's still there. Look!

..and goes.

That's...

Oh, no!

If it doesn't go down in the next minute or so,

there could potentially be a problem.

It's not ready just yet.

It hasn't sunk yet.

Finally, the launch begins.

Five, four,

three, two, one!

Wow, there it goes!

I'm waving goodbye to it on its

four-year mission.

If it works, it'll help scientists gain a better understanding of the Indian Ocean monsoons.

It goes down 1,000 metres and then 2,000 metres

and comes to the surface repeatedly

up to 150 times, for four years solid.

I can just see it. Look!

Just pick her out.

In ten days, it should surface and transmit back to base for the first time.

Only then will the team know if the launch has succeeded.

It's gone!

We're now under way for the southern coast of Zanzibar, the south-western tip of Zanzibar.

A brilliant feeling. You just mention the name Zanzibar to me and I want to go there.

The team takes the opportunity to go ashore.

It's such a public game. Such a great game.

And I think we have a winner.

-Thank you very much.

-Thank you. Very happy with that.

With coastal development and over fishing,

human pressure on this sea is increasing.

So, for the next mission, the team wants to see how that's impacting

one of the ocean's most precious eco-systems.

Environmentalist Philippe heads out with Lucy,

to check on the health of the Indian Ocean's world famous coral reefs.

Worldwide, coral reefs are vital to the lives of a billion people,

who rely on them for food and income.

And they're home to a vast variety of marine life.

But the reefs may have reached a tipping point.

I have to be honest with you, I'm a little disappointed.

I'm not seeing the abundance of fish life that I'd expect here.

It just seems a little light to me and that's kind of disappointing.

For three generations, Philippe's family has been documenting this ocean's threatened habitats.

Having grown up with images of my grandfather's films and my father's films, back in 1948.

You look at that, even though it's in black and white, it's like an amazing forest.

Just richness is unparalleled.

You go back to those places today and it's just a desert.

Coral reefs are disappearing at such a scary rate.

Across the globe, 25% of coral reefs are under threat.

Philippe spots what's attacking this reef -

one of its most voracious predators.

Wow, look at that!

That's a crown-of-thorns, right?

It's enveloping that piece of coral.

A crown-of-thorns starfish eats the coral alive.

They can eat up to 16 or 17, maybe even 18 or more,

square feet of coral reef a year.

You can see right there,

they take their stomach literally and turn it inside out

when they get on the coral

and then start to eject all these stomach enzymes all over it.

And it oozes out all over the coral and liquefy it

and then they just suck it up.

Kind of nasty!

Recently, a hundred fold increase in the numbers

of crown-of-thorns has devastated local reefs.

It may have been caused by people over fishing its predators.

They are very, very prolific.

These guys are just wiping coral out.

But killing crown-of-thorns is tough.

Cut them in two and both halves can survive.

The only ways to get rid of them - inject them with poison,

or bag them up and take them away.

We're going to actually remove these from the reef.

These guys are just wiping coral out.

Look at it reacting!

We're finding more and more of them all over the seabed.

And you can actually just see the way they're moving over the surface of the coral.

Together with other factors like warming seas, this has

contributed to the destruction of over 22% of the reefs

in the south west Indian Ocean alone.

But there is still hope.

Tooni and Philippe head off to discover how damaged coral reefs

could be revived using a new scientific technique.

Leading the work here is Tanzanian scientist, Nsajigwa Mbije.

-Hello, I'm Tooni.

-Tooni, I'm Mbije.

-Philippe.

-Philippe.

-Nice to meet you.

-Thank you for coming.

Hello, everybody. How are you?

Mbije's working on a project around Chumbe, which is just,

to me, a great example of really innovative science.

It's the first time this methodology has been used in the Indian Ocean.

They gear up to visit Mbije's laboratory,

not on land, but about ten metres beneath the water's surface.

Go, Mbije!

Go, Philippe!

It's a facility which could hold an answer to saving the coral reefs.

A man-made coral garden.

What we're looking at here,

is almost the Indian Ocean equivalent of a garden centre.

In this whole nursery, there are about 9,200 individual little pieces of coral.

These little bits of coral or nubbins are taken from a mother colony

from a different location

and moved into this area, where they're basically grown.

It's a little bit like pruning.

The plan is to help save endangered reefs by transplanting living coral into them.

But direct transplantation has had little success.

Mbije and his team are growing young coral in this protected environment,

till it's strong enough to survive being transplanted.

The first thing Mbije does

is collect young coral from a healthy reef.

Then he cuts the coral nubbins off.

Kind of like taking prunings from a tree

and he puts them into these small little rubber tubes.

Although it doesn't look like much, that little section of coral is actually alive.

The coral will grow from what looks like something that potentially doesn't amount to much

and that could spell the survival of the coral reef

in some areas where they've been decimated in the Indian Ocean.

The coral can't be left on its own.

It needs constant care.

So, Mbije's weeding the garden.

This blanketing algae can smother the corals.

So, by removing all of this,

these corals have an opportunity to grow in as healthy a habitat as possible.

Once the nubbins have spent about ten months here, they're ready for transplantation.

If this technique is successful, it could help regenerate damaged reefs,

not just in the Indian Ocean, but across the entire world.

It's really encouraging to see that kind of methodology is actually being used in

areas such as this, where there obviously isn't a huge amount of money to invest in marine science.

But this technique is so simple

and so cheap, basically, it just requires an awful lot of manpower.

We've already lost at least 25% of the world's coral reefs,

so now, because we're taking an active role in their destruction,

this is an opportunity to take an active role in their restoration.

And it's a very hopeful time right now.

As the day ends...

-I planted coral today.

-Yay!

-Fingers of greenness.

It's a chance to plan the next stage of the expedition.

Yeah, so up here... I've not been here before.

This looks fantastic!

People have been living on the shores of the Indian Ocean for over 100,000 years.

How they've related to this vast body of water is the speciality of maritime archaeologist, Lucy Blue.

I'm trying to work out how different people, different cultures

would have approached this sea, this ocean.

Obviously, there are certain parameters they were constrained by, so the winds and the currents...

What were the challenges that they faced?

Trade and migration in the Indian Ocean

has been dominated by the powerful currents that flow

uninterrupted for thousands of miles across it,

before crashing into the East African coast.

This gives you a really good idea of the way the currents are moving along this coastline.

Particularly this East African coastal current or the Zanzibar one.

The combination of the currents and the winds have dictated the way people manoeuvred

around this - particularly this part of the Indian Ocean.

Lucy believes there's much to learn from mankind's battles with these treacherous currents.

So the expedition's heading for a site of particular interest to her.

The wreck of a ship sunk 40 years ago in the unpredictable waters of the Indian Ocean.

To avoid the same fate, the expedition ship will have to be extremely cautious.

When I was talking to the skipper earlier, he was saying this is actually quite a treacherous area

and we're not actually mooring up because the currents are quite complex and unpredictable.

But when they reach the site, they find they aren't the only ones interested in it.

A group of local salvagers are already here,

trying to break up the ship and recover valuable metals.

They're none too pleased to have competition.

All right, folks, we got a bit of a situation out there.

There's a bunch of guys who are trying to cut off the propeller with welding gear.

I don't know whether they think we're going to try and poach their propeller from them,

it's big and its worth a lot of money, but they're protecting themselves with spear guns

and Scotty actually had one of them go to him...

As expedition leader, Paul's worried about the safety his team.

But for Lucy, this is an example of a worldwide problem she often faces.

The destruction of archaeological sites.

There's nothing we can do and if they start ripping off the portholes

and all the rest of it, there's nothing for anybody to see.

-There's nothing for anybody to learn about it.

-I'm actually rooting for them.

-Why?!

-Well, I feel...

-I think we could end up having some contretemps!

I feel the ship is in their waters

and that propeller and any other bits they can use will sustain

their livelihood better than tourists coming to look at it.

I'm not sure about that because you have that thing is there for an instance.

They are going to reap an immediate reward.

It's just condoning that whole activity and encouraging other people

to do it on wrecks throughout the world and then it's gone.

Whichever one of you is right

it's not the immediate problem.

The immediate problem is that they've got spear guns

and they exhibited very threatening behaviour.

The situation is tense.

A crew member who speaks Swahili has gone over to explain

that the team are just here to dive the wreck.

Mike... Mike this is Richard. Come in, over.

We've had a talk with the salvage crew

and they've given us permission to dive on the site.

Mike, that's fantastic.

The salvagers stop diving and the team can get to work.

This is what the salvagers are after,

the remains of the Paraportiani.

Wow, it's absolutely huge!

After 40 years on the bottom,

there's still a lot left of this 94 metre cargo ship.

It's clear from the chains and pulleys that the salvagers are

well on the way to removing the huge bronze propeller.

Bronze scrap is worth thousands of pounds per tonne.

It's going to be a lot of work to shift this.

And ultimately it's setting a precedent for just ripping

shipwrecks apart, regardless of whether they're 40 years old

or 400 years old.

All shipwrecks tell the story of a moment in time when a combination

of circumstances came together to create a catastrophe.

The Paraportiani sunk here in 1967,

early in the evening, carrying wheat from Romania to Jeddah.

The ship was meant to go via the Suez Canal,

but with the Arab-Israeli war in full swing, that was closed

forcing the Paraportiani to travel right round Africa.

For weeks the voyage went well.

Then with just days to go, things went badly wrong.

We believe that they'd lost their radar and their echo sounder

and they were basically travelling in very unfamiliar waters

so they had to resort to compass and sextant and navigating by the stars

in currents which they didn't understand.

Just imagine the sense of terror

coming up on this reef completely lost.

The noise, the panic...

She hit this reef behind us and then broke her back.

Sprawling down here onto the sand.

Somehow, everyone on board, survived,

but the reef and the currents battered and sank the Paraportiani.

Considering she's only been down 40 years there's an amazing amount of marine life down here.

The Paraportiani may be home to many fish, but Lucy is shocked

at how the salvagers are wiping out precious historical information.

I mean, they've got rigs up there, they've got the whole works.

Is it pretty much free game?

It's free game, this is not in the marine reserve area so there's

nothing in terms of the conservation of this particular zone that says...

and anyway, I'd imagine it's very difficult to police.

I know how difficult it is in the UK!

My job, on a daily basis, is trying to battle against the problems

with treasure hunters and salvage work.

When you do meet it face-to-face,

you can't but despise it and everything it represents.

Ten days ago, the expedition launched the Argo float

to monitor the depths of the Indian Ocean.

There it goes! I'm waving goodbye to it. It's a four-year mission.

It's now scheduled to surface and upload its first data,

but has its mission succeeded?

-So this is...

-The moment of truth.

Well it is the moment of truth because with any luck,

if we can get this through we're going to figure out if the Argo

actually worked. So hang on.

-Is that the map?

-That's it.

-That's it! It's a transmit.

-It is!

So it's working?

The map tracks the float's position from where Paul

powered it up, to when it surfaced and successfully uploaded its data.

This must be us going out.

This is when we deployed it and it sank.

And this is it here. It didn't get stuck.

It's going on the expected track which is north and then north west.

It's come up and it's sent the right expected data up.

So do you feel a flutter of pride that it actually worked?

The big thing for me, and it does excite me,

is that it's real-time data so they're all coming up and down

all sending up temperature, salinity, depth and where they are.

For me, it's the fact that there are 3,000 plus

of the Argo floats all over the world.

So our little float is basically

representative of this huge, global data set.

Scientists are already using the data to look into the future and

determine how our oceans and climate might change over the next decade.

With just two days left, the team wants to see how one of the oceans

most elusive residents is faring in these fast changing waters.

The hunt brings them here to the Bazaruto Archipelago,

a chain of islands 20 miles off the coast of Mozambique.

The islands are hammered by the powerful waves and winds that have

shaped these 100-metre high dunes, built up over thousands of years.

You really get a sense of the power of the wind and the ocean here.

Just looking out over the Indian Ocean. Next stop, Australia.

All of that power of the Indian Ocean just slams into this coast

and it kind of stings the back of your legs

like you're getting sandblasted.

Slamming into us at the moment!

The Bazaruto Archipelago acts as a barrier, absorbing the fury

of the Indian Ocean and protecting the 20-mile stretch

of water on the other side.

Tooni believes its here that the team may find a sensitive barometer

of the health of the Indian Ocean, one of its rarest animals.

So this is the dugong, with the best Latin name ever. The Dugong dugong.

A really bizarre hybridisation between the dolphin tail

and then you've got a cow-like/ elephantine front end.

They grow up to about 3.4 metres so they're a fairly decent size.

Dugongs once thrived in this part of the Indian Ocean, but not any more.

Hunting and entrapment in fishermen's nets

have drastically reduced their numbers.

So how well is this tiny population doing?

Right here is pretty much the last viable population of dugong in the western Indian Ocean.

So we've come to this specific area to see if we can find them and,

to be honest, it would be an absolute joy and something really special if we did.

But finding them, I think, is going to be a bit of a nightmare.

Dugongs have always been mysterious.

Their unusual body shape probably inspired the myth of the mermaid.

They have what's called a fusiform body, combining the fluked tail

of a fish with forelimbs and a snout-like head.

This isn't the first time Tooni's searched for them.

She knows how tough it is looking for a few dugongs in a very big ocean.

I spent a month hunting for dugong and I didn't see a single flipping

whisker so if we do see them we are going to be exceptionally lucky.

Ready then, team?

If they can find them it would be a rare chance for Tooni

to see how well they're coping.

They head for an area they've been told has a high density of dugongs,

but Tooni is not convinced.

High density is a bit of misnomer. It's a slightly misleading name.

High density suggests that there's loads of them swimming around but in actual fact that's not true.

It just means that more of them have been spotted in that location than anywhere else.

Tooni still hopes to find a few, but dugongs are notoriously timid.

The plan is to just cut the engines.

It's gonna have to be really, really quiet and a slow operation so we don't freak them out,

cos as soon as they hear the boat noise or hear splashing they're just going to be gone.

If we smell a dugong. it's going to be miraculous.

One of the crew believes they've seen a dugong.

So Tooni takes a chance and jumps in, to try and get close.

But underwater the visibility is terrible.

Finding the dugongs will take more than this.

It just shows how bad the visibility is cos we didn't see diddly.

Paul is going to try and spot them from the air and guide Tooni to them.

These things are really hard to find,

so this is our secret weapon and Tooni's really counting on me

up there. She's counting on me to be able to see them from about 500ft and I can steer her in.

There's a bunch of goats ahead of us.

So what we've got to try and do is

get airborne before we hit any of the goats.

Tooni, Tooni, it's Paul in Victor Charlie here. Copy.

Paul, this is Tooni, over.

We can see you. If you just follow us now, follow this bearing.

Great. Keep us posted. Out.

-Suddenly, Paul sees a grey smudge in the water.

-There's a dugong!

Dugong dugong. Right there!

Just coming around, the wing's in the way but you'll see him in a bit.

We've got a dugong. In fact, there's a small group.

Tooni, Tooni, we are over a group of dugongs.

Get your foot down cos we're over them right now.

That's great news, Paul, great news. We'll make our way towards you now.

We head straight for the aeroplane. Straight for the aeroplane.

I can sense dugong.

I can sense them.

Paul, Paul, which direction are they travelling in? Over.

They're right ahead, right ahead.

They're kind of 2 o'clock running parallel with you.

They're at the surface, they're at the surface.

Oh! I can see them!

Tooni, can you see them? They're right in front of you, over.

Roger that. I can see them, Paul. I can see them.

I'm so happy that we've seen them cos I didn't think we were going to at all, if truth be told.

Seeing the group of dugongs

is positive evidence that the population here is surviving.

But then Paul spots something even more encouraging.

A sign that the dugongs here may be in better shape than they had thought.

And a calf, you see the calf as well? Right there, right there.

Fantastic news! Look at them.

Whoo! Three and a half dugong.

The dugongs are doing more than surviving, they're reproducing.

It's incredibly good news.

How's that, that's all right, isn't it?

The team's success has come just in time.

We're off, we're getting so low on fuel, over.

OK, Paul, thank you so much, we did see the dugong which is absolutely fantastic.

Here we go!

It's the end of their Indian Ocean Odyssey.

It was excellent.

They've journeyed through seas

that supports some of the most varied marine life on the planet.

Diving with the manta rays is one of the finest dives I've ever had.

You know, I've done over 6,000 of them.

The most special part of this expedition, for me,

has been getting a chance to see this part of the world.

The diversity that's here, the diversity of life and abundance of life.

From an ocean perspective, because coral reefs

here in the Indian Ocean are some of the most bio diverse in the world.

Coming on this project and seeing, you know, looking at the marine life

as well as the cultural context

has just reinforced to me how little we know about this ocean.

The Indian Ocean is so rich.

I'm worried about it, though.

So far, the Indian ocean is holding it's own

but in a world that's being transformed so rapidly,

how much longer can it cope?

Next time the team continues to explore the the Indian Ocean.

They'll investigate how marine creatures can help

predict extreme weather.

They'll dive the remains of a medieval village...

See this design here, that's got to be oriental.

And try to protect the largest fish in the sea.

Subtitles by Red Bee Media Ltd

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