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00:00They cover two-thirds of our planet.
00:07They hold clues to the mysteries of our past.
00:12And they're vital for our future survival.
00:18But the secrets of our oceans have remained largely undiscovered.
00:23I am with a six-year-old duck.
00:25Yes! Yes!
00:28Explorer Paul Rose is leading a team of ocean experts
00:32on a series of underwater science expeditions.
00:37For a year, the team has voyaged across the world
00:40to build up a global picture of our seas.
00:43We are doing some pretty uncharted research here.
00:46That is psychedelically awful!
00:49We're here to try and understand the Earth's oceans
00:53and put them in a human scale.
00:57Our oceans are changing faster than ever.
01:00I've never seen ice like this before.
01:04There's never been a better time
01:06to explore the last true wilderness on Earth.
01:10TANZANIA, EAST AFRICA
01:18Tanzania, East Africa.
01:22The team has come to the edge of a continent
01:25where the full force of the Indian Ocean collides with the African coast.
01:31TANZANIA, EAST AFRICA
01:37The Indian Ocean links Africa and Asia.
01:41It has over 44,000 miles of shoreline.
01:47And its coastal waters support habitats
01:50that are home to an enormous diversity of marine life.
01:55But its coasts throng with people.
01:5840 million live along its western edge alone,
02:01making the vibrant coastal waters of this ocean
02:04particularly vulnerable to man's impact.
02:08The sea can never be considered
02:10to be a discrete entity from the land.
02:12The two are completely interconnected
02:14and nowhere more so than the coastal zone.
02:19So the team has come to a place
02:22So the team has come to the rich waters of the Spice Islands,
02:26an intense meeting point of man and sea.
02:32They're here to explore this fragile relationship
02:35and to discover what this ocean can do for man
02:41and what man might be doing to this ocean.
02:45TUNIMATO
02:50Marine biologist and oceanographer Tunimato
02:54will take part in a pioneering experiment
02:57to see how a coastal creature
02:59could help predict natural disasters.
03:03All of this is data
03:06of what's been happening in the ocean and the atmosphere
03:09over the past 40 years or so.
03:13Maritime archaeologist Dr Lucy Blue
03:16will dive a sunken medieval village
03:19to search for evidence that these waters
03:21brought wealth and prosperity.
03:31And environmentalist Philippe Cousteau,
03:34grandson of ocean pioneer Jacques Cousteau,
03:37will discover how man is threatening a coastal giant.
03:42The world's largest fish.
03:46I think it's one of those things like the polar bears
03:50that I want to see before they're gone.
03:55PEMBA
04:09Their first mission is to dive the submerged cliffs
04:13around the island of Pemba.
04:15These rise steeply from the sea floor,
04:18800 metres below,
04:20and are the collision point
04:22for the mighty tides and currents of the Indian Ocean.
04:31This is a very old island that we're on.
04:33It broke away from the mainland 10 million years ago.
04:35So in that 10 million years,
04:37it's just been attacked from all sides by the water currents.
04:40It seems like the perfect place to sort of have a look
04:43at how currents and tides and geology
04:47all interact in one location
04:50and, you know, feel the full force of the ocean.
04:56Toonie and Paul are going to explore a geological feature here,
05:00a submerged fracture scored into the rock.
05:08They want to discover what happens when land and sea collide.
05:14How you doing, Toonie? All right, mate?
05:16Mad! Feel these currents, eh?
05:21They dive down the edge of the island, an underwater cliff face,
05:25to see how the power of the Indian Ocean can shape the land.
05:31This is a rare opportunity.
05:33Behind me, at 800 metres down,
05:36is the bottom of the Pemba-Africa Rift,
05:40which separates this from the continent of Africa.
05:45They soon find the fissure.
05:51A vast crack 30 metres long and 30 metres deep.
06:14This is an erosional feature of this particular fissure.
06:18And what it is, is a weakness in the rock
06:21that's been forced in by continual movement of the water over the years.
06:27The current has just taken us in here.
06:30We're working quite hard to not be pushed too deep into this deep fissure.
06:36And it feels very different to the wall outside.
06:40Even just a casual glance,
06:42you can just see that it's a different life-form inside this fissure.
06:51They've entered an oceanic recess,
06:54an ecosystem teeming with life.
07:01Shoals of sea goldies,
07:03darting mimic blennies,
07:06and two-bar anemonefish.
07:08The same currents that carve the land have brought life to this fissure.
07:13Currents that have travelled thousands of miles across the Indian Ocean.
07:19A lot of these organisms may have arrived
07:22from one of the giant Indian Ocean currents.
07:25Say, for example, a larva started off in Indonesia,
07:28it would have taken about five months to cross the entire Indian Ocean,
07:32right to the east coast of Africa.
07:35And then smacked up against this vertical wall face.
07:38And that's led to this amazing diversity of creatures
07:41and colours and life-forms that you can see.
07:46Deep inside the fissure,
07:48they can see the extent of this stunning vertical reef.
07:52Look at these tree corals!
07:55Normally, sunlight is vital for a healthy reef.
07:59But life here is especially adaptive.
08:02This is the green tree coral, aptly named because it's very dark green.
08:06And the reason why it can grow here and do so well here
08:10is because it doesn't contain any algae at all.
08:13Most corals are half-plant and half-animal,
08:16whereas this one is purely animal.
08:19And it's absolutely beautiful.
08:23Because it contains no algae,
08:25this coral is a natural habitat for many species of fish.
08:29Because it contains no algae,
08:31this coral doesn't depend on sunlight for survival.
08:36Like the rest of the life here,
08:38it feeds on the organisms brought in by the currents.
08:44Most of them are filter-feeding,
08:46which means they're grabbing particles out of the water and feeding on them.
08:51And the reason why there's so many filter-feeding organisms
08:55is because there's so much water being forced in.
08:59Food and nutrients are racing past it,
09:02which is kind of like pizza delivery in an oceanic context.
09:10In contrast to the deep and largely barren open seas,
09:14the collision of land and ocean currents
09:17creates the rich ecosystems that characterise these coastal waters.
09:23You can actually see the currents in action
09:26and how important they are to the marine life of the area,
09:29because without that bringing the larvae of those encrusting organisms,
09:33then there'd be no lifeforms there at all.
09:36These currents help sustain
09:38one of the most important ecosystems in the ocean,
09:41the coral reef.
09:53Coral reefs support a quarter of all fish species
09:57and help support the coastal people here.
10:00But fishing, tourism and pollution are putting reefs under pressure.
10:08So environmentalist Philippe Cousteau
10:11wants to find out if the corals here are healthy.
10:16And one of the best ways to do that is to dive at night.
10:20It brings the coral alive at night in a way that daytime can't.
10:23And to try and... I mean, one of the biggest challenges we always face
10:26is trying to get people to understand that coral reefs are alive,
10:30they're not just rocks.
10:32If you dive the same reef in the daytime and the same reef at nighttime,
10:35it's like diving on two completely separate reefs.
10:43But diving at night can be hazardous.
10:46Night diving is a lot more dangerous,
10:48because you can't see your partner as well if something goes on with lights.
10:51And at night, when it's pitch black underwater,
10:54you can get even confused and turned around about which direction is up.
10:58So if you're running low on air, you don't have any lights.
11:01And if you're going in the wrong direction, it's a bad thing.
11:05They have to prepare quickly for the dive.
11:08In the tropics, night falls fast.
11:11The sun's going down.
11:13And at this latitude, it just drops like a stone.
11:16So I need to get the night dive away right now.
11:19Very messy. Boats alongside here.
11:22And loads of activity. And it's all been sorted out at once.
11:25So I'm in a big push to get everybody off and things out.
11:37At dusk, Toony and Philippe set off to examine the reef.
11:47The next day.
11:57When you point your torch out left, all you see is inky, murky blackness.
12:17Just look. I mean, the size of these table corals are just so big.
12:21It's awesome. It really is.
12:23I have never seen table corals this big in my life.
12:26But you just look up and they're everywhere.
12:32Seeing so many large corals is a positive sign that this reef is healthy.
12:40This right here is such a perfect example.
12:43Of just how vibrant and thick and diverse this whole area is.
12:48I mean, look at this different grouping of corals.
12:53Coral reefs are the most biodiverse ecosystems on the planet.
12:57Even more so than a rainforest.
13:03They're surrounded by many different varieties of coral.
13:06From this favia.
13:08To acropora.
13:13And by diving at night, Philippe and Toony can gauge the health of the coral.
13:19Because the animal part, the polyp, emerges to feed.
13:25One of the reasons I love night dives is because you can really see all of these little arms,
13:30these little tentacles that open up during the night dive.
13:34And during the day those are completely encircled, completely closed,
13:38pulled back into the coral polyp.
13:46Many corals have tentacles armed with stinging cells
13:50that reach out at night to hunt their prey.
13:54Nutrients are transported from the depths by the currents.
13:59But the tidal currents are about to change.
14:01NUTRIENTS ARE TRANSPORTED FROM THE DEPTHS BY THE CURRENTS
14:25But the tidal currents are about to change, and that's worrying Paul.
14:30Dive team, dive team, Kairos, how copy?
14:34There are communication problems.
14:36Dive team, Kairos, how copy?
14:41Strong, strong current, and it's shortly due to change.
14:45Back the other way, so we'll all be affected.
14:48My divers and this ship, we're all going to be affected by these changing currents.
14:53With bad communication as well, and the risks that occur with night diving,
14:59it just gives me the willies a bit, and I do need regular, reliable communication.
15:04I haven't got it in the world.
15:07Underwater, Toony and Philippe are unaware of Paul's concerns.
15:12They've spotted something that could be part of the secret of this reef's success.
15:18So there's two different species of coral growing here,
15:22one of which is a much slower growing species, which is a big coral in the middle.
15:29These two corals are engaged in battle.
15:32What the slower growing coral is doing is emitting toxins via its stinging cells
15:38that prevent the much larger, faster growing table corals from overgrowing it.
15:47Corals use chemical and biological warfare.
15:51By reaching out with their stomachs from within the polyps,
15:55the aggressors can digest their rivals.
16:02During the night, conflicts like these are fought across our oceans,
16:07as corals compete for position and maximum exposure to the sun.
16:15In a coral reef, it's location, location, location.
16:19It's all about where you are.
16:21So these corals are literally battling it out over prime real estate
16:26to try and get access to sunlight.
16:29I love this reef. I love this reef.
16:32It is one of the most incredible reefs I've ever seen.
16:35No question about that.
16:41The nightly battles between different species
16:44prevent any one coral from dominating.
16:49This creates diversity, which helps this reef remain healthy.
16:55A healthy, diverse reef is home to many marine species,
17:00which in turn help feed the people who live on the coast.
17:08It's just so rich and diverse.
17:11All the different kinds of coral.
17:13You can really see them coming out with their little tentacles in the water
17:17and just crying, oh, it's open!
17:18You've just got to put a fist in their face.
17:20They're jumping all over the place.
17:22Yeah, it's not, it's not. Got it. Thank you. Well done.
17:25Watch your feet.
17:26With everyone back on board, Paul leads the expedition south.
17:33They're going to Zanzibar to carry out a pioneering experiment
17:37that could help protect people from the destructive forces
17:40of the extreme weather that can rage in the Indian Ocean.
17:45So all the dive stuff's going to go here?
17:47The dive stuff will be all right there.
17:49It doesn't need to be lashed down because the forecast is good.
17:55The Indian Ocean is the engine
17:57for some of the most unpredictable weather on the planet.
18:01It can trigger floods, droughts and famine.
18:08Heavy rains are caused as warm water evaporates from the surface of the sea,
18:13which can reach 28 degrees centigrade.
18:17The rapid changes in air pressure create spiralling winds.
18:21In extreme conditions, this can produce cyclones.
18:30The waters off Zanzibar might hold information
18:33that could help protect millions of people
18:36against these potentially catastrophic storms.
18:40So the team is about to take part in ground-breaking research
18:44for a climate study.
18:46You're Jens? Yes, I'm Paul.
18:49They'll be working with an international group of coral scientists.
18:55Surprisingly, coral holds a unique record of climate information.
19:00What we're really looking for is to get this boat
19:03just as close in as possible.
19:07So they're going to drill samples of the coral here for the first time.
19:13We have a lot of data from the open ocean,
19:15but we haven't got much data from the African coast.
19:22Paul's seated up and ready to go.
19:24Suni's on the way here.
19:26Yeah, it looks good.
19:29Scientists have realised that as coral grows,
19:32it's affected by different weather conditions.
19:35So its growth pattern over the years creates a record of past climate.
19:42And that could be used to predict future weather.
19:46I'll go down. OK, mate.
19:49Coral grows at about one centimetre a year,
19:52so the larger it is,
19:54Yeah, I got it, Suni.
19:56It's three metres, ten centimetres.
19:59So that lock there is over 300 years old.
20:07Locked inside this coral
20:09is a detailed record of three centuries of local weather.
20:14We've got a perfect 300-year dataset.
20:17And to get that information,
20:19they need to drill a core to the heart of the coral.
20:23Yeah, we've got to steady this drill here,
20:25or it's just going to run around.
20:27Once we get a couple of inches down, it'll steady itself,
20:31but we've got to steady it now.
20:36Coral is one of the most important species in the world,
20:39and it's one of the largest in the world.
20:42Steady it now.
20:47Coral has growth bands within it.
20:49Like tree rings, each band is a year's growth,
20:52so the coral can be aged accurately.
20:57That's the first coral core out.
21:00Got it.
21:01There's the first one.
21:03This is the only live bit of this whole section.
21:06All of this is dead material.
21:09See, that's why this colony can recover quite quickly
21:12from a process that looks quite destructive.
21:15And all of this is data
21:18of what's been happening in the ocean and the atmosphere
21:21over the past roughly 40 years or so.
21:25And in the end, they'll have a whole three metres worth
21:30and a whole 300 years of data.
21:33Should we get this darkened up?
21:35Back on the ship,
21:36Lucy and Philippe are preparing a darkroom to examine the coral.
21:41So apparently this is best if we lay it out,
21:44because you can see the coral.
21:51So far, they've drilled out a 40-year record of the climate.
21:56But to predict the future weather accurately,
21:59they need to go much further back in time.
22:03Right, that is the second piece of coral that we've got.
22:07Hey, here's our number two.
22:09That's our second one.
22:11There's the top.
22:17They'll begin to analyse the centuries of climate information
22:21on board the expedition ship.
22:27That's the live section that we drilled, the bit that we can see.
22:30Oceanographer Craig Grove is using a new technique
22:34to read the weather data from this core with ultraviolet light.
22:39When you get the monsoon coming over,
22:42a large amount of rainfall,
22:44you get these luminescent bandings that occur.
22:47The UV light reveals bright bands which are formed during heavy rains.
22:53Well, the brightest bands indicate the most extreme wet weather.
22:58And that's what we're looking for.
23:00And by counting these bands,
23:03we can date these climate events and when they occur.
23:07So you can find the Raskissimani event.
23:10So we want 1872.
23:131872.
23:15Lucy is keen to see if she can identify one particular cyclone
23:20that wiped out an important trading settlement here.
23:24So they count back almost 140 years along the core.
23:28Are we going to see, what, a wider band or a denser band?
23:31Yeah, well, it depends on the intensity of the rain.
23:34If it was a cyclone, it would be quite bright.
23:37And if it was prolonged, it would be quite wide.
23:40But, oh, well, already you can see
23:42that there's a glow coming straight from that.
23:44That's exactly it, yeah.
23:46It's a really bright, wide band.
23:48Yeah, you can see it, can't you?
23:51That means that there was intense rainfall that year.
23:54No.
23:56That could well be a cyclone.
23:58Well, there you go.
24:00By studying the coral record
24:03to find patterns of extreme weather in the past,
24:06they hope to develop more accurate computer forecasting.
24:14That will help the people living here
24:16by enabling them to prepare for potentially devastating weather.
24:26The team is now heading south
24:28to search for one of the most vulnerable coastal species.
24:34One that lives in shallow mangrove lagoons.
24:38A species at the mercy of an immense global trade.
24:43The seahorse.
24:46Seahorses are getting wiped out in many cases,
24:48all around the world, wherever they can be caught.
24:51So to explore the issue and also contribute a little bit to science
24:56and to conservation science is really special, I think.
25:01In one year, it was estimated
25:03that as many as a quarter of a million seahorses
25:06were exported from Tanzanian waters.
25:10The trade is driven by the huge demand for them
25:13in traditional eastern medicines.
25:15Seahorses are highly prized around the world
25:17for multiple different reasons.
25:18And eastern cultures, you know,
25:20use them for aphrodisiacal properties,
25:23they use them for medicinal, you know, reasons.
25:26So they're being, you know, heavily hunted still around the world.
25:31The team will help assess the impact of the trade
25:34by collecting information about this seahorse population.
25:37Very little is known about either the species that exist here
25:41or the numbers that exist here.
25:43And obviously, with lack of baseline data,
25:45it's then therefore difficult to assess
25:47if these populations are in any way endangered.
25:52Their first task is to find a boat big enough
25:55to take them and their equipment
25:57into the shallow lagoons where the seahorses live.
26:03This sort of thing would probably be quite good.
26:05About the right size, you reckon? Yeah, I think so, don't you?
26:08The waters around the Spice Islands
26:10are home to one of the largest
26:12traditionally made boating fleets in the world.
26:18For maritime archaeologist Lucy, it's like stepping back in time.
26:27It's exactly... This whole tool kit, in fact,
26:30is very akin to what you would find in a medical shipyard.
26:34And the great thing is that they're still building a lot of boats here
26:37and there's obviously a lot of demand.
26:41BELLS RING
26:45With the boat arranged, the team can begin their search for seahorses.
26:54They'll have to bring them out of the water
26:56to take accurate measurements.
26:58A sensitive operation, but important to help protect them.
27:02I'm not a huge fan of taking things out of their environment
27:06into an artificial environment.
27:08So without taking that seahorse out of its environment,
27:11you can't take the measurements that are essential
27:13to look at population and numbers
27:15and therefore you can't go on to make any conservation assessments.
27:27As the divers descend, the lagoon comes alive.
27:34It's a nursery for juvenile scorpionfish,
27:37yellow boxfish,
27:39tiny squid hermit crabs
27:43and a host of mysterious micro-wildlife.
27:47The perfect environment for seahorses.
27:54A few centimetres tall and perfectly camouflaged,
27:57they're not easy to spot.
28:07Back on shore, Paul and Lucy are building a temporary lab.
28:14Here they'll identify the species of any seahorse they find.
28:18The main objective is to shelter it from the sun,
28:22so we need the tarp.
28:24Perfect. And, of course, the wind's from that way as well.
28:31The crayon's broken and the whole thing's ruined here.
28:37OK, you can let go.
28:39It's a tall order, this.
28:41I mean, we've got half a day, roughly,
28:44got about four hours from now,
28:46and then we've got to join Kairos and sail north,
28:50so, I mean, it is a long shot.
28:52There's no doubt about that.
28:58Underwater, the search continues.
29:02Oh, my God!
29:05Judy, over here.
29:07To give you an idea of how hard they are to find,
29:10it is right here.
29:16To disguise themselves,
29:18seahorses allow small organisms to grow on them.
29:22For such a slow-moving fish,
29:24their camouflage is an essential defence against predators.
29:29The only thing that gives her away
29:32is a slight movement of her gills.
29:35She's pumping water through to get oxygen.
29:38And that is pretty much it.
29:42I just think they look so sad.
29:44He's got his little head drooped down.
29:46I know.
29:49She's having a damn good look around, though.
29:52She's got her little head drooped down.
29:55She's having a damn good look around, though.
29:59Now, I'm carefully, carefully going to lift up this seahorse here.
30:06Very gently.
30:08Seahorses almost have a mythical quality.
30:11They look as if they come out of some storybook.
30:16And it might be for this reason
30:18that they are so prized in traditional medicines in the East.
30:26Seahorses are in a lot of trouble.
30:30Look at this beautiful creature.
30:32People capture these in the millions.
30:34I'm not sure if I can get him to hold on to my finger.
30:37There we go.
30:42You need to be very gentle and delicate with him.
30:45What's really key is that we get this one onto shore,
30:50back to its location within 20 minutes,
30:53because we don't want to stress it,
30:55because seahorses are monogamous.
30:58So if this one isn't returned right here,
31:01its mate isn't going to know where it is and it will be lost.
31:07Once the spot is marked, there's no time to waste.
31:11Precious cargo.
31:14There's a tarpaulin there for your gear.
31:20Flip him. Well done.
31:22You've got to be really careful.
31:24She's gone down great.
31:26She's quite big.
31:28Yeah, she's beautiful.
31:30They have just minutes to identify the species.
31:34There she is.
31:36She's in there.
31:37Right, have you started the clock?
31:39Yeah, I have.
31:40Really quiet, really quiet.
31:42So I think she's a female.
31:44Can you see the bands on her?
31:46There's a tail.
31:47Man, she's feisty.
31:48She's great.
31:49Males have a smooth pouch that broods the young,
31:52but females have bands all down their bodies
31:55and a number of them have too small to work in.
31:58broods the young, but females have bands all down their bodies and the number of
32:03these bands helps to identify the species.
32:14Halfway through is ten minutes. 14 millimeters.
32:19Some species of seahorse are traded more than others, so identifying this one will
32:26help determine how endangered the population here is.
32:31It's going to be really hard in the water.
32:32Okay, can you get the pole height?
32:35I just, I've got to get in between your fingers.
32:37Wait, then you're going to have to hold her head and you'll have to get her, hold her tail.
32:42Time is slipping away.
32:45Let's take her out of the water and just do it quickly.
32:47You can do it in the water.
32:49Alright.
32:50You've only got about five minutes left, guys.
32:51Well, then I think the length is the most important one.
32:56The length of the seahorse is a crucial final measurement.
33:00It will confirm the species.
33:02Quickly, get in there.
33:04I can't, I can't with your fingers in.
33:06Alright.
33:08That's perfect.
33:10Can you straighten that baby tail out?
33:12No, it's perfect.
33:14You can run it around the bottom.
33:16Nearly.
33:18I think you got it.
33:20Is that the tip?
33:22Yeah, that's it.
33:24Is that about right?
33:26Shall we go for the upper end then?
33:28Combining these measurements reveals that this is a Hippocampus Bourboniensis,
33:32a species prized in the medicinal trade.
33:36Get your dive gear and we'll bring her out.
33:38Get her when you're ready.
33:40Selling for as much as £500 per kilogram,
33:42this seahorse is at risk from a global trade,
33:46estimated to capture 30 million seahorses a year across 80 countries.
33:53The heart is still going though.
34:09It's so small and yet really, really strong.
34:11Yeah.
34:17As Toonie and Philippe return the seahorse to its exact location,
34:21Lucy and Paul discover something.
34:25Ours is 16.4.
34:27Normally...
34:29Well, it says maximum height 14.
34:31I reckon it's a world beater.
34:33We've got a record.
34:37They've just found the largest Hippocampus Bourboniensis ever recorded.
34:42This vital data will be sent to conservation organisation Project Seahorse.
34:48Identifying where it might be at risk
34:50will be the first step in helping to protect this enigmatic but vulnerable creature.
35:04Earlier in the expedition,
35:06the team found evidence of a cyclone
35:08that hit this region over the weekend.
35:10Paul and maritime archaeologist Lucy
35:12want to explore the remains of a village
35:14that could hold clues to man's long relationship with this sea.
35:20All we need is just one or two...
35:22We're not going to find great big things.
35:24No, no, no.
35:26Something to indicate what's been going on.
35:28Clues, clues.
35:34In 1872,
35:37In 1872,
35:39a cyclone pulverised a coastal village
35:41and dragged it into the ocean.
35:47This is Ras Kissimani,
35:49once a vital trading hub.
35:57They'll be looking for evidence
35:59of its rich trading history.
36:07There's been very limited archaeological work here done before,
36:09although the site has been identified.
36:11But a lot of this material,
36:13because of the effects of the cyclone in 1872,
36:15has effectively been washed into the sea.
36:19So a lot of the material is actually now under the water.
36:21There's very little known about the site.
36:23And so I don't really know what we're going to find.
36:25And so I don't really know what we're going to find.
36:27I'm hoping that we'll find some bits of masonry
36:29and maybe even some pottery
36:31to indicate who was here
36:33and when they settled
36:35and the people they were trading with.
36:37Just to find something.
36:39Absolutely.
36:41Just a small piece,
36:43some small bits of pottery
36:45will be able to give us some idea
36:47of the nature of the activities here.
36:51These underwater remains
36:53have never been studied.
36:55They don't know what, if anything,
36:57they'll find.
36:59It's the challenge of the archaeologists in a way.
37:01Often you don't see a huge amount left on the seabed.
37:04It's a bit like a puzzle in a way.
37:06You have to take bits of the puzzle
37:08and through those clues try and build up a picture.
37:10Enough to give us an indication
37:12of who was settled there,
37:14who they were trading with.
37:16Right, you guys ready?
37:18And I'll hand you the sketch when you get in there.
37:21Five, four, three, two, one.
37:25Diver's in.
37:33The cyclone scattered the remains
37:35across a wide area.
37:37Are you getting anything there?
37:39No, nothing at the moment.
37:41So the best way to cover the ground
37:43is to use underwater scooters.
37:45See this...
37:47Hang on.
37:49Oh, here.
37:51That's it.
37:53Yeah.
37:55At first, it looks like debris and rubble.
37:57Ah, look.
37:59See there?
38:01That shows you the profile
38:03of a bowl.
38:05This is like the local courseware.
38:07So this identifies
38:09the people that were settled at this site.
38:11They found pottery
38:13probably 19th century.
38:15Evidence this is the site
38:18of a sunken village.
38:20Should we go for a scooter round, Lucy?
38:22Yeah, what we need to try and do
38:24is have a look where the main concentration is.
38:34Hey, Paul, Paul, Paul, look.
38:38Oh, wow, what's that?
38:40Oh, wow, look at that.
38:42That is beautiful.
38:44Now, that is a clear import.
38:46I think this is material
38:48that was coming from Persia.
38:50The foliage and glaze
38:52in this design
38:54date it not to the 19th century
38:56but to the 15th.
38:58Evidence that Ras Kisimani
39:00had a much older trading history.
39:02But this is such an identifying
39:04piece of ceramic.
39:06You know, this really gives
39:08an indication of the
39:10history of this place.
39:13It really gives an indication
39:15of the scale of Indian Ocean trade
39:17and the range that people
39:19were travelling.
39:25If you just do a little bit
39:27of hand fanning...
39:29I can't get over how much stuff's here.
39:31Look at this.
39:33I think it's a piece of celadonware
39:35which would have come from
39:37Southeast Asia, maybe even China.
39:39This discovery takes them
39:41even further back in time
39:43and further across this ocean.
39:45That is a beautiful piece.
39:47Celadon
39:49is a type of ancient Chinese pottery.
39:51See this design here?
39:53That's got to be Oriental.
39:55This piece could date to the
39:5714th century and shows
39:59that this village was a trade hub
40:01between China and Africa
40:03over 600 years ago.
40:05You know, this was a major stopping point
40:08on a trading system
40:10along the East African coast.
40:12This particular little site
40:14worked as a sort of stopover,
40:16a service station in a way.
40:18People would come here,
40:20there was a good supply of water
40:22and it all worked as part of
40:24this system of trade along the coast.
40:26Exploiting and extracting
40:28the goods that Africa had to offer.
40:32Laid out on the seabed
40:34is the long history of this village
40:37and the vital role of the Indian Ocean
40:39in uniting cultures through trade.
40:41From 14th century China
40:43to ancient Persia
40:45they have found evidence
40:47that man's been working with this sea
40:49for hundreds of years.
40:57This is the first time
40:59that I've ever dived off an island
41:01in the Indian Ocean
41:03and found such a wealth of material
41:05I mean, the Islamic ceramics
41:07are really rich and colourful
41:09it glazes their colours
41:11and so well preserved
41:13I just cannot get over that.
41:19Across the centuries
41:21the people here harnessed monsoon winds
41:23to drive trade in spices,
41:25gold and even slaves
41:27up and down this coastline.
41:31But these waters
41:34also control the movements of marine life.
41:40Toony and Philippe are on the lookout
41:42for the whale shark
41:44the largest fish in the sea.
41:46We know very very little
41:48about whale sharks
41:50so this is really an attempt
41:52a global attempt
41:54at trying to get an idea
41:56of how many whale sharks are out there
41:58we don't even know that
42:00how they migrate, where they go
42:02These marine giants
42:04are still killed for their meat and fins
42:06and are officially threatened.
42:08Philippe wants to gather
42:10information that can help protect them.
42:14They are still being hunted
42:16and I hope
42:18they won't get wiped out
42:20but I think it's one of those things
42:22like the polar bears
42:24that I want to see
42:26before they're gone.
42:32Giant African river deltas
42:34feed this region of the Indian Ocean
42:36with vast quantities of nutrients.
42:38These wash
42:40into the waters
42:42and create feeding corridors
42:44that draw the whale sharks
42:46to the coastal regions.
42:48Philippe spots
42:50what he's looking for.
42:52There it is!
42:54We got a whale shark!
42:58I keep seeing a little fin
43:01come out of the water
43:03because they stay near the surface
43:05when they're feeding
43:07to take big mouthfuls of krill.
43:09There it is! Good heavens!
43:11It's just come right out of the water
43:13you can see it.
43:15Good lord!
43:17Whale sharks are normally seen
43:19travelling alone
43:21but here a group has gathered.
43:23My goodness!
43:25We are surrounded!
43:27To see six sharks
43:29circling like this
43:31is very rare.
43:33Look at the size of it!
43:35These vast creatures
43:37are almost as big
43:39as the team's boat.
43:47The thing is you read
43:49like eight metre whale sharks
43:51in a book but then you see
43:53an eight metre whale shark
43:56Thuny and Philippe
43:58want to take photographs
44:00of the whale sharks
44:02to identify individuals.
44:04This information will be used
44:06to track whale shark movement
44:08around the globe.
44:10The sharks pose no threat
44:12to humans and as they seem relaxed
44:14the team can go after
44:16the information they need.
44:18The water is clouded
44:20with life.
44:22Shoals of fish
44:24pulse, shimmer
44:26and pool together
44:28for protection.
44:34Mobular rays
44:36glide in
44:38to take advantage
44:40of plentiful prey.
44:43An entire food chain
44:45is active here
44:47and these huge creatures
44:49are cutting swathes
44:51right through its centre.
45:13Whale sharks
45:15can weigh up to
45:1735 tonnes.
45:21They'd be known
45:23to travel distances
45:25of up to 8,000 miles
45:27to recharge
45:29at feeding grounds like this.
45:39The gills
45:42filter the water
45:44of its content.
45:46A cough helps
45:48to clear trapped food particles.
45:54Tiny eyes and poor sight
45:56means it's their sense of smell
45:58that enables them to track down
46:00their prey of fish and plankton.
46:12Their skin
46:14is the thickest
46:16of any animal on earth
46:18and it's the markings
46:20on it that Philippe
46:22needs to photograph.
46:24Like a fingerprint
46:26the spots on the side
46:28of each shark
46:30are unique.
46:33The photographs
46:35will go into a database
46:37to help track the whale sharks
46:39so conservationists
46:41will be able
46:43to track down
46:45their prey
46:47and track down
46:49their prey.
46:51The spots on the side
46:53of each shark
46:55are unique.
46:57The photographs
46:59will go into a database
47:01to help track
47:03the whale sharks
47:05so conservationists
47:07can find out
47:09where they need
47:11to be protected.
47:15That was
47:17incredible!
47:20They are so beautiful!
47:22Giant, gaping
47:24wide mouth!
47:26It was just magical!
47:28Just awesome!
47:36The team moves to land
47:38to get a stable communications platform.
47:42They need to upload
47:44the whale shark photos
47:46into an international database.
47:48This is how they identify them.
47:50The spots on the side of a whale shark
47:52are very similar to fingerprints.
47:54Their spot pattern is different.
47:56It will compare these spots
47:58with a photographic database
48:00of at least a thousand
48:02other whale sharks.
48:04If this shark
48:06has already been identified
48:08in other parts of the world
48:10the database will show
48:12where it's been travelling.
48:14If it's a new shark
48:17it can be tracked.
48:19Right, so here we go!
48:21The results just came up
48:23and we've got a new whale shark!
48:25That's cool!
48:27And the great thing about this
48:29is that we'll find out
48:31if this whale shark
48:33is sighted again.
48:37It's a final success
48:39and a fitting end to the expedition.
48:41The interaction
48:43of land and sea
48:45opens up new trading corridors
48:47that support the whale sharks.
48:51But it also brings
48:53the human activity
48:55that threatens them.
48:57The Indian Ocean
48:59has shown how much
49:01it has to offer
49:03those around it.
49:05But also
49:07how these people
49:09are threatened.
49:11People who've developed
49:14in the sea for centuries.
49:16It's a case of the sea
49:18not dividing but uniting
49:20the different cultures
49:22around its shores.
49:24But we may now be learning
49:26how to work with our coastal waters
49:28strengthening our
49:30fragile relationship with the ocean.
49:44Music
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