Oceans (2008) s01e06 Episode Script

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.
Tanzania, East Africa.
The team has come to the edge of a continent where the full force of the Indian ocean collides with the African coast.
The Indian ocean links Africa and Asia.
It has over 44,000 miles of shoreline, and its coastal waters support habitats that are home to an enormous diversity of marine life.
But its coasts throng with people.
Forty million live along its western edge alone, making the vibrant coastal waters of this ocean particularly vulnerable to man's impact.
The sea can never be considered to be a discrete entity from the land.
The two are completely interconnected, and nowhere more so than the coastal zone.
So the team has come to the rich waters of the spice Islands, an intense meeting point of man and sea.
They're here to explore this fragile relationship and to discover what this ocean can do for man We know so little about these animals.
And what man might be doing to this ocean.
Marine biologist and oceanographer Toni math will take part in a pioneering experiment to see how a coastal creature could help predict natural disasters.
All of this is data on what has been happening in the ocean and the atmosphere over the past 40 years or so.
Maritime archaeologist Dr Lucy Blue will dive a sunken medieval village to search for evidence that these waters brought wealth and prosperity.
Can I say, I can't get over how much stuff's here.
Look at this! And environmentalist Philippe Cousteau, grandson of ocean pioneer Jacques Cousteau, will discover how man is threatening a coastal giant, the world's largest fish.
I think it's one of those things like the polar bears that I want to see before they're gone.
Their first mission is to dive the submerged cliffs around the island of Pombo.
These rise steeply from the sea floor 800 metres below and are the collision point for the mighty tides and currents of the Indian ocean.
This is a very old island that we're on, and it broke away from the mainland 10 million years ago.
So, in that 10 million years, it's just been attacked from all sides by the water currents.
And it seems like the perfect place to sort of have a look at how currents and tides and geology all interact in one location and, you know, feel the full force of the ocean.
Toni and Paul are going to explore a geological feature here, a submerged fracture scored into the rock.
They want to discover what happens when land and sea collide.
How're you doing, Toni? You all right, mate? Man, feel these currents, eh? They dive down the edge of the island, an underwater cliff face, to see how the power of the Indian ocean can shape the land.
This is a rare opportunity.
Behind me, and 800 metres down, is the bottom of the Pombo African Rift, which separates this from the continent of Africa.
They soon find the fissure, a vast crack 30 metres long and 30 metres deep.
This is an embrasure feature, this particular fissure.
What it is, is a weakness in the rock that's been forced in by continual movement of the water over the years.
The current is just taking us in here.
We're working quite hard to not be pushed too deep into this deep fissure.
And it feels very different to the wall outside.
Even just a casual glance, you can just see that it's different life forms inside this fissure.
They've entered an oceanic recess, an ecosystem teaming with life.
Shoals of sea goodies, darting mimic blennies and two bar anemone fish.
The same currents that carve the land have brought life to this fissure.
Currents that have travelled thousands of miles across the Indian ocean.
A lot of these organisms may have arrived on one of the giant Indian Ocean currents.
Say, for example, a larva started off in Indonesia, it would have taken about five months to cross the entire Indian Ocean right to the east coast of Africa, and then smacked up against this vertical wall-face, and that's led to this amazing diversity of creatures and colours and life forms that you can see.
Deep inside the fissure they can see the extent of this stunning vertical reef.
Look at these tree corals.
Normally, sunlight is vital for a healthy reef, but life here is especially adapted to living in the shadows.
This is the green tree coral, aptly named because it's very dark green.
And the reason why it can grow here and do so well here is because it doesn't contain any algae at all.
Most corals are half plant and half animal, whereas this one is purely animal.
And it's absolutely beautiful.
Because it contains no algae, this coral doesn't depend on sunlight for survival.
Like the rest of the life here, it feeds on the organisms brought in by the currents.
Most of them are filter-feeding, which means they're grabbing particles out of the water and feeding on them.
And the reason why there are so many filter-feeding organisms is because there's so much water being forced in.
Food and nutrients are racing past it, which is kind of like pizza delivery in an oceanic context.
In contrast to the deep and largely barren open seas, the collision of land and ocean currents creates the rich ecosystems that characterise these coastal waters.
You can actually see the currents in action and how important they are - to the marine life of the area.
- Mom-hmm.
Because without that bringing the larvae of those encrusting organisms then there'd be no life forms - there at all.
- No.
These currents help sustain one of the most important ecosystems in the ocean, the coral reef.
Thank you, Toni.
Coral reefs support a quarter of all fish species and help support the coastal people here.
But fishing, tourism and pollution are putting reefs under pressure.
So environmentalist Philippe Cousteau wants to find out if the corals here are healthy, and one of the best ways to do that is to dive at night.
It brings the coral alive at night in a way that the daytime can't and to try and I mean, one of the biggest challenges we always face is trying to get people to understand that coral reefs are alive, they're not just rocks.
If you dive the same reef in the daytime, the same reef at night-time, it's like diving on two completely separate different reefs.
But diving at night can be hazardous.
The night-time is a lot more dangerous just because you can't see your partner as well.
If something goes wrong with the lights and at night when it's pitch black underwater, you could get even, you know, confused and turned around about which direction is up.
So if you're running low on air, you don't have any lights You end up going in the wrong direction, and it's a bad thing.
They have to prepare quickly for the dive.
In the tropics, night falls fast.
The sun's going down.
It's going to And at this latitude, it just drops like a stone.
So, I need to get the night dive away right now.
Very messy.
Boats along side here and loads of activity.
And it's all being sorted out at once.
So, I'm in a big push to get everybody off and things happening.
You okay? At dusk, Toni and Philippe set off to examine the reef.
When you point your torch out left, all you see is inky, murky blackness.
Just look, I mean, at the size of these table corals.
They're just so big.
It's awesome! - They're huge! - It really is.
I have never seen table corals this big in my life.
You just look up and they're everywhere.
Seeing so many large corals is a positive sign that this reef is healthy.
This right here is such a perfect example of just how vibrant and thick and diverse this whole area is.
I mean, look at this different grouping of corals.
Coral reefs are the most bio diverse ecosystems on the planet.
Even more so than a rainforest.
They're surrounded by many different varieties of coral, from this Facia to Corpora.
And by diving at night, Philippe and Toni can gauge the health of the coral because the animal part, the polyp, emerges to feed.
One of the reasons I love night dives is because you can really see all of these little arms, these little tentacles.
They open up during the night-time, and during the day, those are completely encircled, completely closed, pulled back into the coral polyp.
Many corals have tentacles armed with stinging cells that reach out at night to hunt their prey.
Nutrients are transported from the depths by the currents.
But the tidal currents are about to change, and that's worrying Paul.
Dive team, dive team, Kayos here, copy.
There are communication problems.
Dive team, Kayos here, copy.
There's a strong, strong current, and it's shortly due to change back the other way, so we'll all be affected.
You know, my divers and this ship are all going to be affected by these changing currents.
With bad communication as well and the risks that occur with night diving, it just gives me the willies a bit.
I do need regular, reliable communication.
I haven't got it at the moment.
Underwater, Toni and Philippe are unaware of Paul's concerns.
They've spotted something that could be part of the secret of this reef's success.
There's two different species of coral growing here.
One of which is a much slower-growing species, which is the big coral in the middle.
These two corals are engaged in battle.
What the slow-growing coral is doing is emitting toxins via its stinging cells, to prevent the much larger, faster-growing table corals from overgrowing it.
Corals use chemical and biological warfare.
By reaching out with their stomachs from within the polyps, the aggressors can digest their rivals.
During the night, conflicts like these are fought across our oceans as corals compete for position and maximum exposure to the sun.
You know, the coral reef, it's location, location, location.
It's all about where you are.
And so these corals are literally battling it out over prime real estate to try and get access to sunlight.
I love this reef.
I love this reef.
It is one of the most incredible reefs I've ever seen.
No question about that.
The nightly battles between different species prevent any one coral from dominating.
This creates diversity, which helps this reef remain healthy.
A healthy, diverse reef is home to many marine species, which, in turn, help feed the people who live on the coast.
- It's just so rich and diverse.
- I know, yeah.
All the different kinds of coral, you could really see them coming out with their little tentacles in the water and those crinoids open You just got a fish in the face.
They're jumping all over the place.
It's not I've got it.
Thank you, well done.
Watch your feet.
With everyone back on board, Paul leads the expedition south.
They're going to Zanzibar to carry out a pioneering experiment that could help protect people from the destructive forces of the extreme weather that can rage in the Indian ocean.
So, all the dive stuff's going to go here.
The dive stuff will be all right there, and it doesn't need to be lashed down because the forecast is good.
The Indian ocean is the engine for some of the most unpredictable weather on the planet.
It can trigger floods, droughts and famine.
Heavy rains are caused as warm water evaporates from the surface of the sea, which can reach 28 degrees centigrade.
The rapid changes in air pressure creates spiralling winds.
In extreme conditions, this can produce cyclones.
The waters off Zanzibar might hold information that could help protect millions of people against these potentially catastrophic storms.
But as the team arrives, their boat is stopped by the port authorities.
The climate study is forced to wait.
We're under pressure to move our boat, the Kayos, into the harbour.
The reason for that is that we've got to have The port authorities want to check we've got all our permits and all our paperwork is straight.
It's gripping stuff, really, because if they don't like us, or if they've had a really, really bad day, and then don't like anybody, that could put a stop on the expedition, I think.
Dead easy.
They could certainly impound the ship.
And that would effectively stop the expedition.
That's a problem.
The authorities escort the team into the harbour at stone Town, the capital of Zanzibar.
Their boat is detained.
They can't continue unless it's released, so expedition leader Paul will have to go ashore to confront the authorities.
Paul and ship's captain Fabric have no idea what to expect.
It's the old story with these trips, some of them just go like clockwork.
Some look like hell, but they all went brilliantly, and there's others the other way around.
You know, there's no control over these situations, and that's difficult, you know.
We've got no control.
Oh, we've got to wait? That's bad news.
Okay, show the, show the Time's getting on.
He If he doesn't get an answer in a few minutes, let's just walk in.
Because at least we're in.
Yeah.
Without the harbour master's stamp on the papers, the expedition is going nowhere.
The enforced stopover means maritime archaeologist Dr Lucy Blue can investigate how this ocean's been used by man for centuries, for trade, transport and as a source of food.
I mean, this has just been like this for Since the Muslims arrived, since people have been trading through Zanzibar, this is what you would expect to see.
It is so rare to find a harbour where, effectively, the majority of boats here are just entirely made out of wood.
They don't have engines in them.
They go out of this harbour and they go up the coast of East Africa and over to Arabia, completely under sail.
Hey, we're in.
Thank you.
Now the whole expedition hangs on Paul's meeting with the harbour master.
Nine crew, huh? She will tell me if you have finished everything.
- Oh, she will tell you.
- Okay, bye.
- Thank you very much.
- Thank you very much.
Thank you very much.
Freedom! The expedition is back on course and the team can finally begin the climate study.
They're about to take part in ground-breaking research to try and predict the violent storms that strike this coastline.
They'll be working with an international group of coral scientists.
Surprisingly, coral holds a unique record of climate information.
What we're really looking for is to get this boat just as close in as possible.
So they're going to drill samples of the coral here for the first time.
We have a lot of data from the open ocean, - but we haven't got much data from - Right.
- From the coast.
- From the African coast.
All suited up and ready to go.
Toni's on the way here.
Yeah, looks good.
Scientists have realised that as coral grows, it's affected by different weather conditions, so its growth pattern over the years creates a record of past climate.
And that could be used to predict future weather.
- I'll go low.
- Okay, mate.
Coral grows at about one centimetre a year, so the larger it is, the older it is.
Yeah, I got it, Toni.
It's three metres, 10 centimetres.
So, that lot there is over 300 years old.
Locked inside this coral is a detailed record of three centuries of local weather.
We've got a perfect 300-year dataset.
And to get that information, they need to drill a core to the heart of the coral.
We've got to steady this drill here or it's just going to run around.
Once we get a couple of inches down, it'll steady itself, but we've got to steady it now.
Coral has growth bands within it.
Like tree rings, each band is a year's growth, so the coral can be aged accurately.
That's the first coral core out.
- Got it! - There's the first one.
This is the only live bit of this whole section.
All of this is dead material.
So you can see that's why this colony can recover quite quickly from a process that looks quite destructive.
And all of this is data on what has been happening in the ocean and the atmosphere over the past roughly 40 years or so.
And in the end, we'll have a whole three metres' worth and a whole 300 years of data.
- Should we get this up? - Yeah, absolutely.
Back on the ship, Lucy and Philippe are preparing a dark room to examine the coral.
So, apparently, this is best if we lay it out.
- All right.
- 'Cause you can see the coral.
So far, they've drilled out a 40-year record of the climate.
But to predict the future weather accurately, they need to go much further back in time.
Right, that is the second piece of coral that we've got! Hey! Here's our number two.
That's our second one.
There's the top.
They'll begin to analyse the centuries of climate information on board the expedition ship.
That's the live section that we drilled, the bit that we can see.
Yeah.
Oceanographer Craig Grove is using a new technique to read the weather data from this core with ultraviolet light.
When you get the monsoon coming over, a large amount of rainfall, you get these luminescent bandings that occur.
Okay.
The Alight reveals bright bands which are formed during heavy rains.
Well, the brightest bands indicate the most extreme wet weather, and that's what we're looking for.
And by counting these bands, we can date these climate events and when they occur.
So, you can find, like, a Raps Kinsman event? So, we want 1872.
1872 Lucy is keen to see if she can identify one particular cyclone that wiped out an important trading settlement here, so they count back almost 140 years along the core.
Are we going to see, what, a wider band or a denser band? Yeah, well, it depends on the intensity of the rain.
If there was a cyclone, it would be quite bright, so And, uh, if it was prolonged, it would be quite wide.
Oh, well, already you can see that there's a glow - coming straight from that.
- Yeah.
- That's exactly it, yeah.
- It's a really bright, wide band.
Yeah, you can see it, can't you? That means that there was intense rainfall that year.
That could well be a cyclone.
There you go.
So, yeah, you can By studying the coral record to find patterns of extreme weather in the past, they hope to develop more accurate computer forecasting.
That will help the people living here by enabling them to prepare for potentially devastating weather.
After hours in the dark room with no air-conditioning, the whole team gets a chance to cool off.
But Paul's mind is elsewhere.
We're going to go early because the crabs come at sunset.
He's heard the biggest land crabs in the world live on a nearby island, so he and Toni are going to see them.
But he's far from relaxed.
He's got this unbelievable fear of beasties.
He doesn't like tentacles or legs.
And there's these very, very large land crabs and we're going to go have a look and see if we can find any of them.
Do you have, um A big machete would be ideal.
A big Or an axe or something, or even - Yes? - A big knife or something.
Perfect! That's perfect.
Ha! - You're welcome.
- Thanks very much, that's great.
Coconut crabs begin life in the ocean before moving on shore.
They weigh up to four kilograms and can have a leg-span of over a metre.
- Hey, Paul.
- Hmm? - I think we should stop here.
- As good a place as any.
It seems like good crab-hunting territory.
Does it? Because they're a prized local delicacy, on some islands, they've been hunted to extinction.
So, Paul and Toni want to find out how healthy this population is.
Hey! Right.
Get some coconut milk spread around, I reckon, 'cause they'll love that.
We're using these 'cause this is their, sort of, preferred food.
Yeah, they love it.
Apparently they can smell it, right? They can scent it.
They'll use infrared light to film undetected.
Can you hear them creeping up on you, there? Well, of course, now we've turned our lights off.
- There's a lot of noise.
- Man, I can hear rustling close.
Can you? Hang on, then.
I tell you what, it's a bit spooky, actually, when there's nothing Can you hear that crinkling? Can you hear the rustling? Oh, my! There's a crab! There's a crab! Look at the size of that beast.
You're dead right.
Is it worth getting up there with our torches and Yeah, yeah.
- Should we go for it? - Yeah.
Okay.
Yeah.
- They're sharing it.
- That's so neat.
Look, they're scraping it out with their claws and then passing it - to their feeding parts.
- Yeah.
The way it's actually wedging itself into the fossilised coral The largest of these creatures can lift weights of up to 28 kilograms.
They are prehistoric-looking creatures, aren't they? Look at them, just, go on, pulling that Look.
Their respiratory organs are in between gills and lungs.
They are a species in mid-evolution, halfway between land and sea.
They've obviously evolved into land crabs, but originally they were brought here on the Indian Ocean currents.
But there's still a direct connection between these and the sea, because when they deposit their larvae, they need to deposit them in the sea and then the larvae grow and develop.
- Yeah.
- And then when the time is right, when they've reached a certain maturation point, they'll come back onto land.
And that's where they'll grow into these that we see here.
Got it.
There are two kinds of these crabs.
There are the blue-coloured ones and the slightly reddish colour.
- Like this guy.
- A very distinctive orange.
And their presence shows that it's actually a very healthy population.
- Oh, does it? - So, they're doing really well here.
- Oh, that's great news.
- Yeah.
The presence of both varieties here means the population is thriving.
That could be a good sign for the species because the larvae produced by this population will be spread by the Indian ocean and could help repopulate other islands.
It's friendlier than I imagined in my nightmares.
Paul Rose, I'm very proud of you.
Land crabs are just one of the species threatened by increasing human pressure along these densely populated coastlines.
The team is now heading south to search for one of the most vulnerable coastal species, one that lives in shallow mangrove lagoons.
A species at the mercy of an immense global trade.
The seahorse.
Seahorses are getting wiped out in many cases, all around the world, wherever they can be caught.
So, to explore the issue and also contribute a little bit to science, and to conservation science, is really special, I think.
In one year, it was estimated that as many as a quarter of a million seahorses were exported from Tanzanian waters.
The trade is driven by the huge demand for them in traditional Eastern medicines.
Seahorses are highly prized around the world for multiple different reasons.
Eastern cultures, you know, use them for aphrodisiacal properties, they use them for medicinal, you know, reasons, so they're being, you know, heavily hunted still around the world.
The team will help assess the impact of the trade by collecting information about this seahorse population.
Very little is known about either the species that exist here or the numbers that exist here.
And obviously, with lack of data it's therefore difficult to assess if these populations are in any way endangered.
Their first task is to find a boat big enough to take them and their equipment into the shallow lagoons where the seahorses live.
This sort of thing would be quite good.
- About the right size, you reckon? - Yeah, I think so, don't you? The waters around the spice Islands are home to one of the largest traditionally-made boating fleets in the world.
For maritime archaeologist Lucy, it's like stepping back in time.
It's just the sort of thing you would find in a medieval shipyard.
And I'm not belittling this actually at all, but it's exactly This whole tool kit, in fact, is very akin to what you would find in a medieval shipyard.
And the great thing is, they're still building a lot of boats here and there's obviously a lot of demand.
With the boat arranged, the team can begin their search for seahorses.
They'll have to bring them out of the water to take accurate measurements.
A sensitive operation, but important to help protect them.
I'm not a huge fan of taking things out of their environment into an artificial environment.
Yet, without taking that seahorse out of its environment, you can't take the measurements that are essential to look at population and numbers, and therefore you can't go on to make any conservation assessments.
As the divers descend, the lagoon comes alive.
It's a nursery for juvenile scorpion fish, yellow box fish, tiny squid, hermit crabs and a host of mysterious micro-wildlife.
The perfect environment for seahorses.
A few centimetres tall and perfectly camouflaged, they're not easy to spot.
Back on shore, Paul and Lucy are building a temporary lab.
Here, they'll identify the species of any seahorse they find.
The main objective is to shelter it from the sun, so we need a tarp.
Perfect.
And, of course, the wind is from that way as well.
Okay, you can let go.
It's a tall order, this.
I mean, we've got half a day, roughly.
Got about four hours from now, and then we got to join Kayos and sail north.
So, I mean, it is a long shot.
There's no doubt about that.
Underwater, the search continues.
Oh, my God! Toni, over here.
To give you an idea of how hard they are to find, it is right here.
To disguise themselves, seahorses allow small organisms to grow on them.
For such a slow-moving fish, their camouflage is an essential defence against predators.
The only thing that gives her away is the slight movement of her gills, which she's pumping water through to get oxygen, and that is pretty much it.
I just think they look so sad.
He's got his little head drooped down.
Oh, yeah.
She's having a damned good look around, though.
Now, I'm carefully, carefully going to lift up this seahorse here.
Very gently.
Seahorses almost have a mythical quality.
They look as if they've come out of some story book.
And it might be for this reason that they are so prized in traditional medicines in the East.
Seahorses are in a lot of trouble.
Look at this beautiful creature.
People capture these in the millions.
I'm not sure if I can get him to hold on to my finger.
There we go.
Need to be very gentle and delicate with him.
What's really key is that we get this one onto shore, back to its location, within 20 minutes because we don't want to stress it.
Because seahorses are monogamous, so if this one isn't returned right here, its mate isn't going to know where it is and it'll be lost.
Once the spot is marked, there's no time to waste.
Precious cargo.
- Yeah, I got it.
- Got it? Okay, there's a tarpaulin there for your gear.
Flipping well done.
Got to be really careful.
Aw, she's gone down, great.
- She's quite big.
- Yeah, she's beautiful.
They have just minutes to identify the species.
Here you go, she's in there.
- Have you started the clock? - We've got to be really quiet.
- Yeah, I have.
- Really quiet.
Really quiet, yeah? I think she's a female.
You can see the bands on her.
- There's the tape, yep.
- Man, she's feisty.
She's great.
Males have a smooth pouch that broods the young, but females have bands all down their bodies and the number of these bands helps to identify the species.
Five, six, seven, eight, nine, 10,1.
Eleven.
You're halfway through.
It's 10 minutes.
Fourteen millimetres.
Now, that's a lot.
That's spot on.
Some species of seahorse are traded more than others, so identifying this one will help determine how endangered the population here is.
Hold her like that.
It's going to be really hard underwater.
Okay, can you get Can you get this Quickly.
Toni, I got to get in between your fingers.
Then you're going to have to You're going to have to I'll have to hold her head and you'll have to get her Hold her tail.
Time is slipping away.
Let's take her out of the water and just do it quickly.
- You can do it in the water.
- All right.
You've only got about five minutes left, guys, as far as The length of the seahorse is a crucial final measurement.
It will confirm the species.
Quick, get in there.
I can't.
I can't with your fingers there.
All right.
That's perfect.
Can you straighten that baby tail out? - She's strong.
- You can run it round the bottom.
- Nearly.
- We've got the end.
- I think you've got it.
- Yeah, you got the end.
- You got the tip? - Yeah, that's it, right.
- Good.
- All right.
164, is that about right? So that's Should we go for the upper end, then? Combining these measurements reveals that this is a Hippocampus borboniensis, a species prized in the medicinal trade.
Get your dive gear, we'll bring her out.
- Right.
- Call when you're ready.
Selling for as much as 500 pounds per kilogram, this seahorse is at risk from a global trade, estimated to capture 30 million seahorses a year across 80 countries.
My heart is still going, though.
They're so small, and they're really, really strong.
Yeah.
As Toni and Philippe return the seahorse to its exact location, Lucy and Paul discover something.
But ours is 16.
4.
Normally Well, it says, "Maximum height, 14.
" I reckon it's a world beater! We got a record! They've just found the largest Hippocampus borboniensis ever recorded.
This vital data will be sent to conservation organisation, Project seahorse.
Identifying where it might be at risk will be the first step in helping to protect this enigmatic but vulnerable creature.
Earlier in the expedition, the team found evidence of a cyclone that hit this region over 100 years ago.
Paul and maritime archaeologist Lucy want to explore the remains of a village that could hold clues to man's long relationship with this sea.
- All we need is just one or two - Yeah, I know.
We're not going to find great, big things.
No, no, no, it's just, sort of - Something to indicate - Clues, clues, yes.
In 1872, a cyclone pulverised a coastal village and dragged it into the ocean.
This is Ras Kisimani, once a vital trading hub.
They'll be looking for evidence of its rich trading history.
There's been very limited archaeological work done here before, although the site has been identified.
But a lot of this material, because of the effects of the cyclone in 1872, has effectively been washed into the sea.
So, a lot of the material's actually now under the water.
There's very little known about the site.
- Okay.
- And so I don't really know what we're going to find.
I'm hoping that we'll find some bits of masonry and maybe even some pottery to indicate who was here and when they settled and, you know, the people they were trading with, so It would be great just to find something, wouldn't it? Oh, no, absolutely, absolutely, because, I mean, just a small piece, you know, some small bits of pottery will be able to give us some idea of the nature of the activities here.
These underwater remains have never been studied.
They don't know what, if anything, they'll find.
It's the challenge of the archaeologist in a way.
Often you don't see a huge amount left on the seabed.
And it's a question It's a bit like a puzzle, in a way.
You have to take bits of the puzzle and through those clues, try and build up a picture, enough to give us an indication of who was settled there, who they were trading with.
Right, you guys ready, and I'll hand you the scooters when you get in there, all right? Five, four, three, two, one, divers in.
The cyclone scattered the remains across a wide area.
- You getting anything there? - No, nothing at the moment.
So the best way to cover the ground is to use underwater scooters.
See this, um Oh, hang on.
There's nothing.
Oh, here, Lucy, stop.
What's this? Yeah.
At first, it looks like debris and rubble.
Ah, look.
See there? That shows you the profile of a bowl.
So, this is like the local cause ware.
So, this identifies the people were settled at this site.
They've found pottery, probably 19th century.
Evidence this is the site of the sunken village.
Should we go for a scoot around, Lucy? Yeah, what we need to try and do is have a look at where the main concentration is.
Hey, Paul, Paul, Paul, look! Oh, wow, what's that? Wow, wow, look at that! That is beautiful.
Now, that is a clear import.
I think this is material that was coming from Persia.
The foliage and glaze in this design date it not to the 19th century, but to the 15th.
Evidence that Ras Kisimani had a much older trading history.
This is such an identifying piece of ceramic, you know.
This really gives an indication of the scale of Indian Ocean trade and the range that people were travelling.
If you just do a little bit of hand fanning I can't get over how much stuff's here.
Look at this! I think it's a piece of celadon ware, which would have come from, sort of, Southeast Asia, maybe even China.
This discovery takes them even further back in time and further across this ocean.
That's a beautiful piece.
Celadon is a type of ancient Chinese pottery.
See this design here? That's got to be Oriental.
This piece could date to the 14th century and shows that this village was a trade hub between China and Africa over 600 years ago.
You know, this was a major stopping point on a trading system along the East African coast.
This particular little site worked as a sort of stopover, a service station in a way, you know, people would come here, there was a good supply of water, and it all worked as a part of this system of trade along the coast.
It makes a lot of sense.
Exploiting and extracting the goods that Africa had to offer.
Laid out on the seabed is the long history of this village and the vital role of the Indian ocean in uniting cultures through trade.
From 14th century China to ancient Persia, they have found evidence that man has been working with this sea for hundreds of years.
This is the first time that I've ever dived off an island in the Indian Ocean and found such a wealth of material, particularly of this period.
I mean, the Islamic ceramics are really rich and colourful, their glazes, their colours, you know.
And they're just so well preserved.
I just can't get over that.
Across the centuries, the people here harnessed monsoon winds to drive trade in spices, gold and even slaves up and down this coastline.
But these waters also control the movements of marine life.
Toni and Philippe are on the lookout for the whale shark, the largest fish in the sea.
We know very, very little about whale sharks.
So, this is really an attempt, a global attempt, at trying to get an idea of, A, how many whale sharks are out there.
We don't even know that.
How they migrate, where they go We don't know, really, anything.
These marine giants are still killed for their meat and fins and are officially threatened.
Philippe wants to gather information that can help protect them.
They are still being hunted, and I hope they won't get wiped out, but I think it's one of those things like Like the polar bears, that I wanna see before they're gone.
Giant African river deltas feed this region of the Indian ocean with vast quantities of nutrients.
These wash into the waters and create feeding corridors that draw the whale sharks to the coastal regions.
Philippe spots what he's looking for.
There it is.
We got whale shark! Oh, yeah, yeah, yeah Just keep seeing a little fin come out of the water.
'Cause they stay near the surface when they're feeding.
They come to take big mouthfuls of krill.
- There it is.
Good heavens! - My goodness! It's just come It's just come right out the water.
You can see it.
Good lord.
Whale sharks are normally seen travelling alone, but here, a group has gathered.
My goodness, we are surrounded.
To see six sharks circling like this is very rare.
Look at the size of it.
These vast creatures are almost as big as the team's boat.
Thing is, you read, like, "Eight-metre whale shark" in a book, but then you see an eight-metre whale shark and it's That thing was huge.
Toni and Philippe want to take photographs of the whale sharks to identify individuals.
This information will be used to track whale shark movement around the globe.
The sharks pose no threat to humans, and as they seem relaxed, the team can go after the information they need.
The water is clouded with life.
Shoals of fish pulse, shimmer and pool together for protection.
Mobile rays glide in to take advantage of plentiful prey.
An entire food chain is active here, and these huge creatures are cutting swathes right through its centre.
Whale sharks can weigh up to 35 tons.
They've been known to travel distances of up to 8,000 miles to recharge at feeding grounds like this.
The gills filter the water of its content.
A cough helps to clear trapped food particles.
Tiny eyes and poor sight means it's their sense of smell that enables them to track down their prey, fish and plankton.
Their skin is the thickest of any animal on earth, and it's the markings on it that Philippe needs to photograph.
Like a fingerprint, the spots on the side of each shark are unique.
The photographs will go into a database to help track the whale sharks so conservationists can find out where they need to be protected.
That was That was incredible! They are so beautiful! - Oh, it was incredible.
- Giant, gaping, wide mouth.
It was just magical, just awesome.
The team moves to land to get a stable communications platform.
They need to upload the whale shark photos into an international database.
This is how they identify them.
The spots on the side of a whale shark are very similar to fingerprints, unique in every single whale shark, their spot pattern is different.
It'll compare these spots with a photographic database of at least, you know, a thousand other whale sharks.
If this shark has already been identified in other parts of the world, the database will show where it's been travelling.
If it's a new shark, then one more can be tracked.
Right, so here we go.
The results just came up and We've got a new whale shark.
That's cool.
- That is cool.
- Well done.
And the great thing about this is that we'll find out We'll be e-mailed if this whale shark is sighted again and where it was sighted.
- That's great.
- If our whale shark It's a final success and a fitting end to the expedition.
The interaction of land and sea created the feeding corridors that support the whale sharks.
But it also brings the human activity that threatens them.
The Indian ocean has shown how much it has to offer those around it.
- That's a really bright band.
- Yeah, you can see it, can't you? But also how these people are putting it under pressure.
People who have developed ways of exploiting this sea for centuries.
It's a case of the sea not dividing, but uniting the different cultures around its shores.
But we may now be learning how to work with our coastal waters, strengthening our fragile relationship with the ocean.
Next time, the team explores the blue waters of the Mediterranean sea.
They'll brave perilous caves for proof of its turbulent past.
This cave is like a time capsule.
They'll look for evidence of one of Europe's first superpowers.
Going in.
And they'll search for the feared great white shark.