Bbc.Okeany.E06.Pribrezhnye.Vody.Indijskogo.Okeana
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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.
13:58But 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.
31:33Males have a smooth pouch that broods the young,
31:37but females have bands all down their bodies
31:40and the numbering is社
32:00Females have bands all down their bodies and the number of these bands helps to identify the species.
32:20Some species of seahorse are traded more than others,
32:23so identifying this one will help determine how endangered the population here is.
32:30It's going to be really hard in the water.
32:42Time is slipping away.
32:44Let's take her out of the water and just do it quickly.
32:47You can do it in the water. You've only got about five minutes left, guys.
32:56The length of the seahorse is a crucial final measurement.
33:00It will confirm the species.
33:08That's perfect.
33:10Can you straighten that baby tail?
33:13You can run it round the bottom. Nearly.
33:17I think you've got it.
33:27Combining 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.
33:39Selling for as much as £500 per kilogram,
33:43this seahorse is at risk from a global trade
33:46estimated to capture 30 million seahorses a year across 80 countries.
33:53The start is still going, though.
34:07It's so small and yet really, really strong.
34:10Yeah.
34:16As Toonie and Philippe return the seahorse to its exact location,
34:20Lucy and Paul discover something.
34:24Ours is 16.4.
34:26Normally...
34:28Well, it says maximum height 14.
34:30I reckon it's a world beater.
34:33We've got a record.
34:36They've just found the largest Hippocampus bourboniensis ever recorded.
34:46This vital data will be sent to conservation organisation Project Seahorse.
34:51Identifying where it might be at risk
34:54will be the first step in helping to protect this enigmatic but vulnerable creature.
35:06Earlier in the expedition, the team found evidence of a cyclone
35:10that hit this region over 100 years ago.
35:13Paul and maritime archaeologist Lucy
35:16want to explore the remains of a village
35:19that could hold clues to man's long relationship with this sea.
35:23All we need is just one or two...
35:26We're not going to find great big things, are we?
35:29No, no, no. It's just sort of...
35:31Something to indicate what's been going on.
35:33Clues, clues.
35:37In 1872, a cyclone pulverised a coastal village
35:42and dragged it into the ocean.
35:47This is Ras Kissimani,
35:49once a vital trading hub.
35:58They'll be looking for evidence of its rich trading history.
36:06There's been very limited archaeological work here done before,
36:09although the site has been identified.
36:11But a lot of this material, because of the effects of the cyclone in 1872,
36:15has effectively been washed into the sea.
36:18So a lot of the material is actually now under the water.
36:22There's very little known about the site,
36:24and so I don't really know what we're going to find.
36:26I'm hoping that we'll find some bits of masonry
36:29and maybe even some pottery
36:32to indicate who was here and when they settled
36:35and the people they were trading with.
36:37It would be great just to find something, wouldn't it?
36:39Oh, no, absolutely. Absolutely.
36:41Because, I mean, just a small piece, some small bits of pottery
36:44will be able to give us some idea of the nature of the activities here.
36:52These underwater remains have never been studied.
36:56They don't know what, if anything, they'll find.
36:59It's the challenge of the archaeologists, in a way.
37:02Often you don't see a huge amount left on the seabed,
37:04so it's a bit like a puzzle, in a way.
37:06You have to take bits of the puzzle and, through those clues,
37:09try and build up a picture,
37:11enough to give us an indication of 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.
37:20All right.
37:21Four, three, two, one.
37:25Diver's in.
37:28The cyclone scattered the remains across a wide area.
37:32Are you getting anything there?
37:34No, nothing at the moment.
37:36So the best way to cover the ground is to use underwater scooters.
37:41See this, um... Hang on.
37:44Yeah, there's nothing.
37:47Oh, here. Look, see? Stop.
37:49That's it. Yeah.
37:51At first, it looks like debris,
37:54Ah, look. See there?
37:57That shows you the profile of a bowl.
38:00So this is like the local courseware.
38:03So this identifies the people that were settled at this site.
38:08They found pottery, probably 19th century.
38:11Evidence this is the site of the sunken village.
38:14Shall we go for a scooter round, Lucy?
38:16Yeah, what we need to try and do is have a look
38:18where the main construction site is.
38:22Hey, Paul, Paul, Paul, look.
38:25Oh, wow, what's that?
38:27Oh, wow, look at that.
38:30That is beautiful.
38:35Now, that is a clear import.
38:38I think this is material that was used to make pottery.
38:42I don't know.
38:44I don't know.
38:46Now, that is a clear import.
38:49I think this is material that was coming from Persia.
39:07But this is such an identifying piece of ceramic.
39:10You know, this really gives an indication
39:13of the scale of Indian Ocean trade
39:16and the range that people were travelling.
39:24If you just do a little bit of hand fanning...
39:27I can't get over how much stuff's here. Look at this.
39:31I think it's a piece of celadonware,
39:33which would have come from the South East Asia, maybe even China.
39:38This discovery takes them even further back in time
39:42and further across this ocean.
39:45That's a beautiful piece.
39:47Celadon is a type of ancient Chinese pottery.
39:51See this design here? That's got to be Oriental.
39:54This piece could date to the 14th century
39:57and shows that this village was a trade hub
40:00between China and Africa over 600 years ago.
40:04You know, this was a major stopping point
40:07on a trading system along the East African coast.
40:10This particular little site worked as a sort of stopover,
40:14a service station, in a way.
40:16People would come here, there was a good supply of water,
40:20and it all worked as part of this system of trade along the coast.
40:24It's exploiting and extracting the goods that Africa had to offer.
40:30Laid out on the seabed is the long history of this village
40:34and the vital role of the Indian Ocean in uniting cultures through trade.
40:39From 14th-century China to ancient Persia,
40:42they have found evidence that man's been working with this sea
40:46for hundreds of years.
40:49This is the first time that I've ever dived off an island in the Indian Ocean
40:54and found such a wealth of material, particularly of this period.
40:58I mean, the Islamic ceramics are really rich and colourful.
41:02It glazes their colours, you know, and so well-preserved.
41:06I just... I cannot get over that.
41:08Across the centuries, the people here harnessed monsoon winds
41:12to drive trade in spices, gold and even slaves
41:16up and down this coastline.
41:21But these waters also control the movements of marine life.
41:29This is the first time that I've ever been in the Indian Ocean.
41:33They also control the movements of marine life.
41:39Tuni and Philippe are on the lookout for the whale shark,
41:42the largest fish in the sea.
41:46We know very, very little about whale sharks,
41:49so this is really an attempt, a global attempt,
41:51at trying to get an idea of, A, how many whale sharks are out there.
41:55We don't even know that.
41:57How they migrate, where they go, we don't know really anything.
42:03These marine giants are still killed for their meat and fins
42:06and are officially threatened.
42:09Philippe wants to gather information that can help protect them.
42:14They are still being hunted.
42:16And I hope they won't get wiped out,
42:19but I think it's one of those things like the polar bears
42:24that I want to see before they're gone.
42:29Giant African river deltas feed this region of the Indian Ocean
42:34with vast quantities of nutrients.
42:37These wash into the waters and create feeding corridors
42:41that draw the whale sharks to the coastal regions.
42:47Philippe spots what he's looking for.
42:50There it is.
42:52We've got a whale shark!
42:54We've got a whale shark!
42:57Oh, yeah, yeah, yeah.
42:59I keep seeing a little fin come out of the water
43:01because they stay near the surface when they're feeding.
43:04They come to take big mouthfuls of krill.
43:07There it is. Good heavens.
43:09It's just come right out of the water. You can see it.
43:13Good Lord.
43:17Whale sharks are normally seen travelling alone,
43:20but here a group has gathered.
43:23My goodness, we are so brandish.
43:28To see six sharks circling like this is very rare.
43:32Look at the size of it!
43:35These vast creatures are almost as big as the team's boat.
43:47The thing is, you read, like, eight-metre whale sharks in a book,
43:50but then you see an eight-metre whale shark and it's...
43:53The thing was huge.
43:57Thuny and Philippe want to take photographs of the whale sharks
44:00to identify individuals.
44:03This information will be used
44:05to track whale shark movement around the globe.
44:10The sharks pose no threat to humans,
44:13and as they seem relaxed,
44:15the team can go after the information they need.
44:21The water is clouded with life.
44:24Shoals of fish pulse, shimmer and pool together for protection.
44:35Mobular rays glide in to take advantage of plentiful prey.
44:41An entire food chain is active here,
44:44and these huge creatures are cutting swathes right through its centre.
45:11Whale sharks can weigh up to 35 tonnes.
45:19They've been known to travel distances of up to 8,000 miles
45:23to recharge at feeding grounds like this.
45:27The gills filter the water of its content.
45:31A cough helps to clear trapped food particles.
45:38Tiny eyes and poor sight means it's the only place
45:41where whale sharks can be found.
45:46The whale sharks are also known to be very sensitive.
45:51Tiny eyes and poor sight means it's their sense of smell
45:55that enables them to track down their prey, fish and plankton.
46:21Their skin is the thickest of any animal on Earth,
46:25and it's the markings on it that Philippe needs to photograph.
46:42Like a fingerprint, the shark's skin is the only thing
46:47Like a fingerprint, the spots on the side of each shark are unique.
46:56The photographs will go into a database to help track the whale sharks,
47:00so conservationists can find out where they need to be protected.
47:17That was incredible.
47:19They are so beautiful.
47:21That was incredible.
47:22Giant, gaping, wide mouth.
47:25It was just magical, just awesome.
47:35The team moves to land to get a stable communications platform.
47:41They need to upload the whale shark photos into an international database.
47:48This is how they identify them.
47:49The spots on the side of a whale shark are very similar to fingerprints,
47:52unique in every single whale shark.
47:54Their spot pattern is different.
47:55It will compare these spots with a photographic database
47:59of at least a thousand other whale sharks.
48:05If this shark has already been identified in other parts of the world,
48:09the database will show where it's been travelling.
48:14If it's a new shark, then one more can be trapped.
48:19Right, so here we go.
48:20The results just came up and we've got a new whale shark.
48:25That's cool.
48:26Well done.
48:27And the great thing about this is that we'll find out,
48:30it will be emailed if this whale shark is sighted again and where it was sighted.
48:34That's great.
48:35If our whale shark is sighted.
48:37It's a final success and a fitting end to the expedition.
48:42The interaction of land and sea created the feeding corridors
48:46that support the whale sharks.
48:51But it also brings the human activity that threatens them.
48:57The Indian Ocean has shown how much it has to offer those around it.
49:01It's a really bright band.
49:02Yeah, you can see it, can't you?
49:05But also how these people are threatened.
49:11People who've developed ways of exploiting this sea for centuries.
49:16It's a case of the sea not dividing but uniting the different cultures around its shores.
49:24But we may now be learning how to work with our coastal waters,
49:28strengthening our fragile relationship with the ocean.
49:34MUSIC
50:04.