0:00:02 > 0:00:05They cover two thirds of our planet.
0:00:07 > 0:00:11They hold clues to the mysteries of our past.
0:00:11 > 0:00:16And they're vital for our future survival
0:00:16 > 0:00:21but the secrets of our oceans have remained largely undiscovered
0:00:21 > 0:00:23until now.
0:00:23 > 0:00:28- I am with a six gill shark.- Yes, yes!
0:00:28 > 0:00:32Explorer Paul Rose is leading a team of ocean experts
0:00:32 > 0:00:36on a series of underwater science expeditions.
0:00:36 > 0:00:41For a year the team has voyaged across the world to build up
0:00:41 > 0:00:43a global picture of our seas.
0:00:43 > 0:00:46We are doing some pretty uncharted research here.
0:00:46 > 0:00:51- That is psychedelically powerful! - We're here to try and understand
0:00:51 > 0:00:54the earth's oceans and put them in a human scale.
0:00:58 > 0:01:00Our oceans are changing faster than ever.
0:01:00 > 0:01:02I've never seen ice like this before.
0:01:02 > 0:01:05There's never been a better time
0:01:05 > 0:01:10to explore the last true wilderness on earth.
0:01:18 > 0:01:22Eritrea, East Africa.
0:01:22 > 0:01:25The team is heading to the southern Red Sea.
0:01:25 > 0:01:29I feel like I'm a kid again. You know, you say can you smell the sea?
0:01:31 > 0:01:35The Red Sea is technically an ocean because it was formed when
0:01:35 > 0:01:40the continents of Africa and Asia tore apart millions of years ago.
0:01:40 > 0:01:44Unlike the tourist diving Mecca to the north,
0:01:44 > 0:01:47the southern part remains remote and untouched.
0:01:49 > 0:01:51By and large this is unexplored.
0:01:51 > 0:01:55It's uncharted territory, particularly under the water.
0:01:56 > 0:02:00The southern Red Sea is one of the most important marine sites
0:02:00 > 0:02:01in the world.
0:02:02 > 0:02:05Home to a spectacular array of species,
0:02:05 > 0:02:08many found nowhere else on earth.
0:02:10 > 0:02:13The team has come here to discover how this small sea
0:02:13 > 0:02:18could hold clues to the future of all our oceans.
0:02:23 > 0:02:25Environmentalist Philippe Cousteau Jr
0:02:25 > 0:02:29wants to investigate whether these waters,
0:02:29 > 0:02:32some of the warmest on earth, could help our oceans cope
0:02:32 > 0:02:35with the threat of global warming.
0:02:35 > 0:02:37We need to figure something out
0:02:37 > 0:02:39that is going to help all the other coral in the world.
0:02:39 > 0:02:45This sea is one of the most significant in human history.
0:02:45 > 0:02:50Maritime archaeologist Dr Lucy Blue is searching for evidence
0:02:50 > 0:02:52that it was here that early modern humans
0:02:52 > 0:02:56first left Africa and populated the planet.
0:02:56 > 0:02:57Well, that's fantastic.
0:02:57 > 0:03:03Marine biologist and oceanographer Tooni Mahto wants to witness
0:03:03 > 0:03:06something fundamental about our oceans...
0:03:06 > 0:03:08How they're born.
0:03:08 > 0:03:11If you don't dive in the Red Sea, all you see is...
0:03:11 > 0:03:13that. That's all you see.
0:03:13 > 0:03:15You see blueness.
0:03:15 > 0:03:19To understand anything about what happens in our planet's oceans,
0:03:19 > 0:03:20you have to get in.
0:03:26 > 0:03:27But 30 years of war
0:03:27 > 0:03:32have kept this unique stretch of sea virtually inaccessible.
0:03:32 > 0:03:36Now for the first time, an expedition like this
0:03:36 > 0:03:38has been allowed in.
0:03:41 > 0:03:45Hello, sir. Very good to meet you. My name is Paul.
0:03:45 > 0:03:49Well, this is just one little bit of paper but it means a lot to us.
0:03:49 > 0:03:51I mean there it is, that's our permit.
0:03:51 > 0:03:53It's a single permit and it took us
0:03:53 > 0:03:55ten months to get this thing,
0:03:55 > 0:03:58but it doesn't give us any protection against
0:03:58 > 0:04:01any of the other things that are probably going to go wrong.
0:04:01 > 0:04:04This is definitely an ambitious expedition.
0:04:04 > 0:04:05No doubt about it.
0:04:06 > 0:04:07For the first mission,
0:04:07 > 0:04:11Tooni and Philippe will investigate how our oceans formed.
0:04:14 > 0:04:16They're heading south to Djibouti,
0:04:16 > 0:04:20a country at the gateway of the Red Sea.
0:04:20 > 0:04:24Here the world map is being re-drawn
0:04:24 > 0:04:27as a completely new ocean is created.
0:04:29 > 0:04:33I'm fascinated by how the earth looks today
0:04:33 > 0:04:35and why it looks today the way it does,
0:04:35 > 0:04:39and I'm also fascinated by this idea that actually the land is moving,
0:04:39 > 0:04:42is constantly moving, constantly changing.
0:04:42 > 0:04:46But to actually go and experience that I think is, is really key.
0:04:48 > 0:04:53Right here beneath this bay, huge tectonic forces have formed
0:04:53 > 0:04:55a crack beneath the earth's crust
0:04:55 > 0:04:59pulling apart the plates of Africa and Arabia.
0:04:59 > 0:05:02That process forms all our oceans
0:05:02 > 0:05:04but this is one of the only places
0:05:04 > 0:05:06in the world where you can dive
0:05:06 > 0:05:08and see it in action.
0:05:08 > 0:05:12We've come here to witness something that's really, really special.
0:05:12 > 0:05:17We're hoping to basically witness the birth of an ocean, because...
0:05:17 > 0:05:21it is literally where a new ocean will form over millions of years.
0:05:21 > 0:05:24So it's splitting the land apart?
0:05:24 > 0:05:27It's splitting the land apart and this area will one day flood
0:05:27 > 0:05:30with water from the Indian Ocean and the Red Sea,
0:05:30 > 0:05:33so we will be over two completely separate land masses
0:05:33 > 0:05:36- that are moving away from each other.- Are we going to be able to...
0:05:36 > 0:05:40- How close are they together? Do we know?- I don't know. Time will tell.
0:05:40 > 0:05:42I want to see if I can touch two continents at once.
0:05:53 > 0:05:57On the seabed, they're looking for the opening, or rift.
0:05:57 > 0:05:59Go that way.
0:06:01 > 0:06:03I think it's over here.
0:06:06 > 0:06:09An incredibly dark opening.
0:06:09 > 0:06:14At least that's my impression of what a rift should look like.
0:06:14 > 0:06:15Ladies first!
0:06:15 > 0:06:17I'm going down.
0:06:18 > 0:06:22Descending into the rift that has opened up.
0:06:26 > 0:06:31They dive down, disappearing between Africa and Arabia.
0:06:35 > 0:06:38It just drops down into complete nothingness.
0:06:40 > 0:06:43Not quite what I expected at all.
0:06:45 > 0:06:50It's a tight squeeze through some of these passages.
0:06:50 > 0:06:52Gotta be really careful.
0:06:56 > 0:07:00This rift has been formed by the action of the earth literally
0:07:00 > 0:07:02ripping itself apart.
0:07:02 > 0:07:06Just think of the amount of force that it would have taken.
0:07:06 > 0:07:11The narrowness of the rift shows that it's right at the beginning
0:07:11 > 0:07:14of a process that will continue for millions of years.
0:07:14 > 0:07:18Normally it's happening thousands of metres down
0:07:18 > 0:07:22so it's extremely rare to see this so close to the surface.
0:07:24 > 0:07:28As the rift widens, magma from beneath the earth's crust
0:07:28 > 0:07:31rises and solidifies to form a new ocean floor,
0:07:31 > 0:07:35gradually pushing the plates further apart.
0:07:35 > 0:07:38Let's put a hand on one continent each.
0:07:38 > 0:07:44I've got, I've got the Somalia plate on the end of my finger,
0:07:44 > 0:07:46and this is the African plate,
0:07:46 > 0:07:49and Philippe to the right has got the Arabian plate.
0:07:53 > 0:07:56Between us we're actually spanning two continents.
0:07:56 > 0:08:01Over time, these two bits of rock will move away from each other.
0:08:01 > 0:08:05They're moving at a rate of about two centimetres a year
0:08:05 > 0:08:07which is about the same rate as a nail growth.
0:08:07 > 0:08:14In millions of years, this gap could be as wide as the Atlantic.
0:08:14 > 0:08:18So this could be New York and that could be London.
0:08:18 > 0:08:25As these plates pull apart, water floods in, creating the new ocean.
0:08:25 > 0:08:29Not many people get to be at the site of a new ocean.
0:08:29 > 0:08:32It's like seeing how the Red Sea once was.
0:08:32 > 0:08:37It's a pretty remarkable feeling, the beginning of an ocean.
0:08:44 > 0:08:47It's stunning. The reality of it is that
0:08:47 > 0:08:49those two bits will never touch again,
0:08:49 > 0:08:52and will keep on moving and moving for pretty much eternity.
0:08:56 > 0:08:58Millions of years from now,
0:08:58 > 0:09:03hundreds of square miles could be covered by water,
0:09:03 > 0:09:06the new ocean, and it's already been named...
0:09:06 > 0:09:08the Afar.
0:09:10 > 0:09:12Tooni and Philippe are heading back
0:09:12 > 0:09:15to rejoin the expedition in Eritrea.
0:09:19 > 0:09:20The plan is to sail north
0:09:20 > 0:09:25to discover why the Red Sea is so important in our history.
0:09:27 > 0:09:32And how its marine life could help all our oceans survive.
0:09:32 > 0:09:35But as one of the first teams allowed in here,
0:09:35 > 0:09:38nothing is straightforward.
0:09:38 > 0:09:40Hello!
0:09:40 > 0:09:43'Fuel is rationed in this country,'
0:09:43 > 0:09:46and the Nemo is full and we need another 5,000 litres
0:09:46 > 0:09:47to complete the mileage.
0:09:47 > 0:09:50I'm calling again about our fuel.
0:09:50 > 0:09:54The Navy have given us a huge amount of support
0:09:54 > 0:09:57and they're going to put one of their people on board.
0:09:57 > 0:09:59Hello, good to meet you.
0:09:59 > 0:10:02You look after us and we'll look after you, how's that?
0:10:03 > 0:10:06It's not long before he needs to help out.
0:10:06 > 0:10:09Just need a bit of a hand to see if...
0:10:09 > 0:10:12Filming's barely begun before soldiers put a stop to it.
0:10:12 > 0:10:16We don't want to film their... the ship or anything...
0:10:16 > 0:10:19From the BBC Oceans expedition.
0:10:19 > 0:10:20Oh, it is confirmed.
0:10:20 > 0:10:23We can have the 5,000 litres. Well, that's fantastic.
0:10:24 > 0:10:28With enough fuel promised for the journey, it's time to leave port
0:10:28 > 0:10:30and head off for the next target.
0:10:33 > 0:10:36It's a two-hour trip east,
0:10:36 > 0:10:39and many thousands of years back in time.
0:10:39 > 0:10:41She's flying!
0:10:46 > 0:10:49Recent findings suggest this
0:10:49 > 0:10:52was one of the first seas early modern humans ever saw
0:10:52 > 0:10:56before making their way out of Africa and across the globe.
0:10:59 > 0:11:01For maritime archaeologist Dr Lucy Blue,
0:11:01 > 0:11:06it's a rare chance to investigate such ancient human activity.
0:11:08 > 0:11:11I think it's really important, because people
0:11:11 > 0:11:14don't really understand the first time people encountered the sea,
0:11:14 > 0:11:16or what they did when they got there,
0:11:16 > 0:11:19and this is some of the earliest evidence that there is
0:11:19 > 0:11:22for early modern humans settling in a coastal environment.
0:11:24 > 0:11:26Lucy is hoping to find clues preserved here
0:11:26 > 0:11:30about the first encounters our ancient ancestors had
0:11:30 > 0:11:32with the Red Sea.
0:11:34 > 0:11:36I'm really finding it fascinating.
0:11:36 > 0:11:40It's like a big jigsaw and you've got all these little pieces that,
0:11:40 > 0:11:43well not many of them, actually, to put into the puzzle.
0:11:43 > 0:11:44And... I'm really...
0:11:44 > 0:11:47and I'm also interested in the nature of the finds
0:11:47 > 0:11:50because they are very different to what you find on most sites.
0:11:50 > 0:11:52You've haven't got ceramics or building remains.
0:11:52 > 0:11:54It's a different type of site.
0:11:55 > 0:11:58The hostilities may be over, but this is still
0:11:58 > 0:12:03very much a military zone and access is heavily restricted.
0:12:03 > 0:12:06Soldiers watch their every move.
0:12:06 > 0:12:09Wow, there's a lot of military bases there, aren't there?
0:12:09 > 0:12:11All of that is the military encampment.
0:12:11 > 0:12:14Pretty good guns up on top there, Lucy.
0:12:14 > 0:12:16There's a bit of waving, let's wave back.
0:12:16 > 0:12:17It's always a good thing.
0:12:21 > 0:12:26Normally, they'd have to dive down to the sea bed to look for clues
0:12:26 > 0:12:28but here the sea floor has come to them.
0:12:29 > 0:12:33Over thousands of years, earthquakes have raised up
0:12:33 > 0:12:36the ancient coral reef by ten metres.
0:12:36 > 0:12:41With it, a slice of history that's 125,000 years old
0:12:41 > 0:12:44has been pushed into daylight.
0:12:45 > 0:12:46This is all old coral. I mean,
0:12:46 > 0:12:47Look at some of this.
0:12:47 > 0:12:51If there's any doubt about whether that's coral or not, you know...
0:12:51 > 0:12:53Buried in this ancient coral,
0:12:53 > 0:12:57they're hoping to find evidence of early modern human activity.
0:12:57 > 0:13:00What we need is some sort of... just chuck a load of water onto it.
0:13:08 > 0:13:11Hey, Lucy! Look at that. That bit.
0:13:11 > 0:13:13Oh, yeah, that's more like it.
0:13:13 > 0:13:16- That's got to be.- You've really got to, that's fantastic.- Look at that.
0:13:16 > 0:13:18- Oh, that's beautiful. - Give it a spray.
0:13:18 > 0:13:21That's what we're looking for.
0:13:21 > 0:13:24- It's an ancient hand blade. - That can take skin off, no problem.
0:13:24 > 0:13:27Well, be careful because you can and that's part of the reason
0:13:27 > 0:13:31that we can tell it's not been moved you know by water action or the sea.
0:13:31 > 0:13:35It's been deposited here in its original context because
0:13:35 > 0:13:36it's still pretty sharp.
0:13:36 > 0:13:39See how, if you hold it that way it doesn't feel quite right.
0:13:39 > 0:13:44Hold it this way, you see that's curving down and this is curving up
0:13:44 > 0:13:47- so depending what you were going to do with it...- Yeah, that's true.
0:13:47 > 0:13:51Because look at that, that shape. That is a proper beautiful tool.
0:13:51 > 0:13:52That's beautiful.
0:13:52 > 0:13:56This type of tool, made from volcanic glass called obsidian,
0:13:56 > 0:14:00dates from the middle Palaeolithic period.
0:14:00 > 0:14:03There's no other obsidian here, so it must have come here
0:14:03 > 0:14:05through some sort of human action.
0:14:05 > 0:14:09So early modern humans were definitely here
0:14:09 > 0:14:14but is there evidence of their relationship with the sea?
0:14:14 > 0:14:17- I think that's maybe what we've been looking for!- Yep.
0:14:17 > 0:14:20They've found what appears to be an ancient oyster bar.
0:14:25 > 0:14:30Imagine if you're shucking all these oysters. Look how well that fits in.
0:14:30 > 0:14:34You know, just... it just fits perfect, doesn't it?
0:14:34 > 0:14:37So you can just imagine this whole area where people have come,
0:14:37 > 0:14:40they've collected the shells, they've processed them,
0:14:40 > 0:14:44they've eaten them and they've just thrown them on the floor
0:14:44 > 0:14:46and I think that's just, it's just fantastic.
0:14:46 > 0:14:48You can see it in such a distinct horizon.
0:14:50 > 0:14:52Early modern humans were probably
0:14:52 > 0:14:56driven from the central plains of Africa by drought.
0:14:56 > 0:14:59They would have stumbled across the Red Sea
0:14:59 > 0:15:01in their search for food and water.
0:15:01 > 0:15:04It's very significant in a lot of ways
0:15:04 > 0:15:08because it shows one of the first, if not the first, bits of evidence
0:15:08 > 0:15:13that we have for human interaction with the sea here on the Red Sea.
0:15:15 > 0:15:18It's a really...
0:15:18 > 0:15:24exciting feeling to hold some tools and the last man to use this...
0:15:24 > 0:15:26was 125,000 years ago.
0:15:29 > 0:15:34These tools show how our ancestors learned to exploit the Red Sea.
0:15:34 > 0:15:36For the first time
0:15:36 > 0:15:40they had a food source that didn't rely on the climate.
0:15:42 > 0:15:46And when sea levels dropped, these thriving coastal people
0:15:46 > 0:15:49had the opportunity to cross this narrow sea
0:15:49 > 0:15:54out of Africa and eventually populate the entire world.
0:16:03 > 0:16:07The Red Sea has always been a critical point of communication
0:16:07 > 0:16:12and trade and transportation, but I hadn't, until today, appreciated how
0:16:12 > 0:16:16incredibly early that communication and contact with the sea started.
0:16:16 > 0:16:18It just gives it such depth.
0:16:23 > 0:16:24That's the past.
0:16:24 > 0:16:28But it's what the Red Sea could tell us about the future of our oceans
0:16:28 > 0:16:32that's brought environmentalist Philippe Cousteau here,
0:16:32 > 0:16:38particularly his concern for coral reefs, the rain forests of the sea.
0:16:41 > 0:16:44Probably one of the most critical issues that ocean conservation
0:16:44 > 0:16:48is facing over the next decade or so is the loss of coral reefs.
0:16:50 > 0:16:53Coral is vital to the health of the ocean,
0:16:53 > 0:16:55harbouring a huge diversity of life.
0:16:57 > 0:17:00But rising sea temperatures across the world
0:17:00 > 0:17:03are causing much of it to suffer from bleaching...
0:17:03 > 0:17:06to turn white and die.
0:17:06 > 0:17:12Of all the coral reefs in the world, we've lost about 25% - are gone.
0:17:12 > 0:17:14Another 25% are heavily threatened
0:17:14 > 0:17:17and we fear will be gone within the next 50 years or so.
0:17:22 > 0:17:27The Red Sea is the perfect place to study the impact of warming seas.
0:17:27 > 0:17:31Water temperatures here are among the hottest on earth,
0:17:31 > 0:17:34reaching 34 degrees Centigrade.
0:17:37 > 0:17:42We've got the monitor right here and we're going to submerge it maybe...
0:17:42 > 0:17:45ten metres underwater, about 30 feet.
0:17:45 > 0:17:48It's winter now and Philippe wants to find out
0:17:48 > 0:17:51what the corals are dealing with.
0:17:51 > 0:17:55The temperature reads 27.8 degrees Celsius, almost 28 degrees Celsius.
0:17:55 > 0:17:56That is too warm.
0:17:56 > 0:17:59That's just not an optimal temperature range.
0:17:59 > 0:18:01You know it's winter time.
0:18:01 > 0:18:05Winter, I don't like to see this so I'm concerned about what's going on.
0:18:06 > 0:18:11Joining Philippe is Eritrean marine scientist, Yonathan Bockre,
0:18:11 > 0:18:16one of the few people to have spent any time on these reefs.
0:18:16 > 0:18:21I know basically, you know, the coral types here
0:18:21 > 0:18:24so this is a great opportunity for me.
0:18:24 > 0:18:28Yonathan thinks there's something surprising about this coral,
0:18:28 > 0:18:31and the team is now keen to investigate.
0:18:31 > 0:18:35I've been dreaming of getting into the Red Sea all my life,
0:18:35 > 0:18:39so the chance to do so now is pretty spectacular.
0:18:39 > 0:18:43And then to be able to do it here in Eritrea where few people
0:18:43 > 0:18:49have ever dived before, let alone filmed before, is...
0:18:49 > 0:18:55is probably one of the most exciting dives of my life.
0:18:55 > 0:18:58With such high winter temperatures,
0:18:58 > 0:19:02there could be a lot of bleached coral.
0:19:07 > 0:19:11I can feel the water. I almost don't need a wet suit, it's so warm.
0:19:15 > 0:19:21It is looking pretty beautiful... What a relief!
0:19:21 > 0:19:26Astonishingly, the coral is far from dead.
0:19:26 > 0:19:28It's flourishing.
0:19:28 > 0:19:33I'm so amazed at how healthy this coral looks.
0:19:33 > 0:19:34In all my experience,
0:19:34 > 0:19:38this coral should not be thriving the way it is.
0:19:40 > 0:19:44You see all the fish swimming in the water column
0:19:44 > 0:19:48and that's the symbol of a healthy, healthy reef.
0:19:50 > 0:19:53The first thing we need to do is to see what's down here and where it is.
0:19:53 > 0:19:56It's just so full of stuff here.
0:19:56 > 0:20:00It's really hard to do this because everything is overlapping.
0:20:00 > 0:20:04It's so dense and so rich it's actually quite difficult to map.
0:20:06 > 0:20:11Coral reefs are the life support system of our oceans.
0:20:11 > 0:20:17Without them a quarter of all known fish species would be under threat.
0:20:19 > 0:20:24There are small patches of bleached coral here
0:20:24 > 0:20:27but according to Eritrean scientist, Yonathan Bockre,
0:20:27 > 0:20:33even these damaged corals recover faster than you'd expect.
0:20:33 > 0:20:36What is so unique about these corals is that
0:20:36 > 0:20:40even in the extremely high water temperature, they manage to survive.
0:20:42 > 0:20:44Anywhere else in the world,
0:20:44 > 0:20:47these conditions would spell disaster for the corals.
0:20:47 > 0:20:50Something very unusual is happening here.
0:20:50 > 0:20:54- It's important to find out what because it might just help
0:20:54 > 0:21:00other coral reefs avoid the ravages of global warming.
0:21:00 > 0:21:03The water is really, really warm.
0:21:03 > 0:21:05There's no way, in my experience,
0:21:05 > 0:21:09that that coral should be doing that well, but it is.
0:21:09 > 0:21:12We need to figure something out that is going to help
0:21:12 > 0:21:14all the other coral in the world,
0:21:14 > 0:21:17and if it's possible to do that here,
0:21:17 > 0:21:20this place is like a gold, solid gold mine.
0:21:20 > 0:21:25I mean this is a gold coral because, it's platinum, diamond coral,
0:21:25 > 0:21:28it's so valuable because if this holds that secret...
0:21:28 > 0:21:30then there's hope.
0:21:30 > 0:21:32To understand what's going on,
0:21:32 > 0:21:35they need to take small samples of the coral.
0:21:46 > 0:21:50Here you go. That's plenty, that's all we need from this one.
0:21:51 > 0:21:56Coral is a complex organism that's both plant and animal.
0:21:56 > 0:22:02Inside the animal part, the polyp, is a type of plant known as algae.
0:22:02 > 0:22:05It's this algae that gives the coral its colour
0:22:05 > 0:22:09and provides vital energy through photosynthesis.
0:22:09 > 0:22:13When water temperatures get too high, typically what happens -
0:22:13 > 0:22:17the coral loses the algae. The algae is stressed to such a degree
0:22:17 > 0:22:19that it leaves the coral skeleton.
0:22:20 > 0:22:23This is coral bleaching.
0:22:23 > 0:22:26So the secret of these corals' ability to survive
0:22:26 > 0:22:32must have something to do with the type of algae that lives within it.
0:22:32 > 0:22:36One of the theories as to why this coral is able to survive
0:22:36 > 0:22:38in such high temperature water
0:22:38 > 0:22:41is that it harbours a specific heat-tolerant algae.
0:22:44 > 0:22:47The special heat-resistant algae
0:22:47 > 0:22:51could be what's keeping this coral so vibrantly alive.
0:22:51 > 0:22:57It may be adapting to rising sea temperatures.
0:22:57 > 0:22:59If so, this Red Sea coral
0:22:59 > 0:23:03could hold the key to helping the rest of the world's coral too.
0:23:05 > 0:23:11The hope is that if we can isolate that algae, we could potentially
0:23:11 > 0:23:14grow it in the laboratory and literally inoculate
0:23:14 > 0:23:18other coral reefs around the world, so that when they bleach,
0:23:18 > 0:23:22this algae can move in and the corals can survive.
0:23:22 > 0:23:27It may sound like science fiction but leading coral scientists agree
0:23:27 > 0:23:31that heat-tolerant algae might one day provide a way
0:23:31 > 0:23:34to protect corals worldwide.
0:23:34 > 0:23:38I'm going to put that pyrites in there...
0:23:38 > 0:23:42I think it's mind-boggling to think that it's samples like these
0:23:42 > 0:23:45that could hold the key to global coral conservation.
0:23:45 > 0:23:49As climate change is encroaching, sea temperatures are rising,
0:23:49 > 0:23:51there's a lot of concern and...
0:23:51 > 0:23:55whatever is making these corals tick, hopefully it is this algae.
0:23:55 > 0:23:58Whatever it is, it's very exciting.
0:23:59 > 0:24:02The investigation doesn't finish here.
0:24:02 > 0:24:08There are more mysteries within the coral but they can only be revealed
0:24:08 > 0:24:09under cover of darkness.
0:24:09 > 0:24:13While they wait, Lucy and Philippe
0:24:13 > 0:24:15have been invited to the nearby island.
0:24:15 > 0:24:18That would make an excellent frame in a boat.
0:24:18 > 0:24:22A limited resource is being destroyed by Cousteau.
0:24:23 > 0:24:28They're going to have a lesson in traditional Egyptian bread-making.
0:24:28 > 0:24:30It's something very unique to each country.
0:24:30 > 0:24:33I've never even heard of cooking bread in sand. I love it!
0:24:44 > 0:24:47It smells so good.
0:24:47 > 0:24:50- It's not every day you get to make bread on a beach, is it?- No!
0:24:52 > 0:24:55Now that it's dark, they can dive.
0:24:55 > 0:24:58They're looking for evidence of another way
0:24:58 > 0:25:02these corals might cope with the extreme conditions here...
0:25:03 > 0:25:09a mysterious phenomenon which causes some corals to fluoresce, or glow.
0:25:11 > 0:25:14It'll be a complicated dive.
0:25:14 > 0:25:19Normally when we're on a night dive, we've got a nice bright, white light.
0:25:19 > 0:25:21But so that if there's any fluorescence at all,
0:25:21 > 0:25:24to help us see it, we've got these flashy blue lights
0:25:24 > 0:25:28and it's the blue lights that will help us see the fluorescence
0:25:28 > 0:25:31but of course they have to turn the white ones off.
0:25:31 > 0:25:35So that's where it kind of doubles up the risk factor. We can't quite see.
0:25:36 > 0:25:38Nobody has ever had a chance
0:25:38 > 0:25:42to look for fluorescing coral in these waters before.
0:25:42 > 0:25:46As a marine biologist, Tooni will be the first.
0:25:46 > 0:25:49Scientists have a difficult time of getting here
0:25:49 > 0:25:51as it's so logistically difficult
0:25:51 > 0:25:55and it's so un-dived that if we do get to see fluorescent pigments,
0:25:55 > 0:25:59I think it will be a first for me to see them full stop,
0:25:59 > 0:26:01and a first in Eritrean waters as well,
0:26:01 > 0:26:03so it's a real kind of double winner.
0:26:03 > 0:26:07Three, two, one...
0:26:07 > 0:26:08go!
0:26:10 > 0:26:14There's no way of knowing what to expect.
0:26:14 > 0:26:18They may see none at all.
0:26:18 > 0:26:23OK, so these are sort of our sci-fi glasses, I guess, aren't they?
0:26:24 > 0:26:28The yellow goggles filter out specific wavelengths of light
0:26:28 > 0:26:32to help them see if any of the corals here do fluoresce.
0:26:32 > 0:26:34The blue light's on.
0:26:41 > 0:26:45With a regular dive torch, this is what you see.
0:26:47 > 0:26:51But with blue light and yellow goggles.
0:26:51 > 0:26:54Oh, look at that! It does work.
0:26:56 > 0:26:58Wow!
0:26:58 > 0:27:01It just jumps out at you instantly, doesn't it?
0:27:05 > 0:27:07As soon as you put the torch on,
0:27:07 > 0:27:10it just picks out different spots of coral.
0:27:10 > 0:27:12I've never seen anything like it.
0:27:12 > 0:27:15It reminds me of a 1980s disco.
0:27:23 > 0:27:28This extraordinary phenomenon is produced by fluorescent pigments
0:27:28 > 0:27:31found in the tissues of a variety of coral species.
0:27:31 > 0:27:33That's, like, multi-coloured.
0:27:35 > 0:27:38There's a huge amount...
0:27:38 > 0:27:40of fluorescence on the reef.
0:27:41 > 0:27:44I think we're freaking some of the fish out
0:27:44 > 0:27:46with our blue lights, by the way.
0:27:46 > 0:27:49Why corals fluoresce is a scientific mystery
0:27:49 > 0:27:52but it might be one way they've evolved to deal
0:27:52 > 0:27:56with the intensity of the sunlight that's bombarding them.
0:27:56 > 0:27:58One school of thought is that it's likely
0:27:58 > 0:28:02the fluorescent pigments in this particular coral we're looking at
0:28:02 > 0:28:05has a protective function from the very, very strong sunlight.
0:28:05 > 0:28:09The fluorescent pigments might be screening out
0:28:09 > 0:28:14some wavelengths of light, acting almost like a sunscreen.
0:28:16 > 0:28:20If these fluorescent pigments are actually protecting the coral algae
0:28:20 > 0:28:22from sun damage, then it means that
0:28:22 > 0:28:26there's a very good chance that these corals will remain healthy.
0:28:28 > 0:28:32The large amount of fluorescence could be another reason
0:28:32 > 0:28:35why these corals are coping in these hot waters.
0:28:37 > 0:28:41The marvels of the Red Sea...
0:28:41 > 0:28:43never cease to amaze.
0:28:46 > 0:28:49- Tooni, what do you reckon? - That was so cool.
0:28:49 > 0:28:54But to me it was more like why it's working, why it's important,
0:28:54 > 0:28:58all the wonderful things that are happening in the sea that we don't understand,
0:28:58 > 0:29:01we don't have a clue about, that's the power of it for me.
0:29:01 > 0:29:04There's another secret bit to the recipe of survival.
0:29:04 > 0:29:07It doesn't give up its secrets easily, that reef.
0:29:07 > 0:29:10Time to break the Egyptian bread.
0:29:10 > 0:29:11Make sure there's no sand in it.
0:29:11 > 0:29:14You have to bury it so you build a fire,
0:29:14 > 0:29:17- and then it goes down to the embers.- We built the fire.
0:29:17 > 0:29:20And for the bread to break Tooni.
0:29:20 > 0:29:22I've just cracked a filling.
0:29:22 > 0:29:23You've just cracked a filling?
0:29:23 > 0:29:26- Just cracked a tooth. - It's a little hard.
0:29:26 > 0:29:28There's no need to be rude, now!
0:29:28 > 0:29:31I've just cracked a tooth.
0:29:31 > 0:29:35There's no shortage of skills an expedition leader needs.
0:29:35 > 0:29:39- I might, I might put a temporary filling on there.- Have you got a...
0:29:39 > 0:29:41I do, yeah.
0:29:41 > 0:29:43I'm not a trained dentist
0:29:43 > 0:29:45but I have had some training by the Royal Air Force,
0:29:45 > 0:29:49some years ago, so, so I've had some practice.
0:29:49 > 0:29:50When you say some years ago...
0:29:50 > 0:29:54That was in '91 I had the training, come to think of it.
0:29:54 > 0:29:57- Let me just have a look... - OK, where you do want me?
0:29:57 > 0:30:00Just open up and lean back a bit if you can.
0:30:01 > 0:30:04This is an old tube, it's all we've got.
0:30:04 > 0:30:06Does that hurt?
0:30:06 > 0:30:08Don't move, don't move.
0:30:12 > 0:30:14It doesn't look too bad, you know?
0:30:14 > 0:30:19Sorry, Tooni. Didn't want to push the...
0:30:19 > 0:30:21- Thanks, man.- All right, well done.
0:30:23 > 0:30:26- Blimey, sweating bullets!- Me too.
0:30:30 > 0:30:34Today, it's time to leave Eritrea and head north to Sudan
0:30:34 > 0:30:39to continue the exploration of this untouched part of the Red Sea,
0:30:39 > 0:30:41but there are fuel problems again.
0:30:41 > 0:30:43We're trying to hurry things up here.
0:30:43 > 0:30:46It's late, we're... it's an hour late.
0:30:46 > 0:30:49Haven't got much of a back-up plan.
0:30:49 > 0:30:53If the fuel doesn't arrive, we'll be stuck in these waters.
0:30:53 > 0:30:55As expeditions like this are so rare,
0:30:55 > 0:30:57the send-off has become a local event.
0:30:57 > 0:30:59INAUDIBLE
0:31:02 > 0:31:05We've been over-run by, by officials today.
0:31:05 > 0:31:09It's all important. We've now got the British Ambassador arriving.
0:31:09 > 0:31:11I'm going to go present my credentials.
0:31:13 > 0:31:16- Hello, I'm Paul Rose. Nice to meet you.- Pleased to meet you.
0:31:16 > 0:31:18- How you doing, all right?- Very well.
0:31:18 > 0:31:22- Would you like some tea or something? - I'd love a cup of tea.- Great, OK.
0:31:22 > 0:31:27At last the promised fuel arrives.
0:31:27 > 0:31:29We've got the fuel, thank heavens.
0:31:29 > 0:31:31Yeah, I was very, very pleased there to see the truck,
0:31:31 > 0:31:34so pleased to see the truck that I temporarily forgot
0:31:34 > 0:31:39to check that it's the right fuel for us.
0:31:39 > 0:31:43It's, this fuel is marine diesel, yeah?
0:31:43 > 0:31:49With the right fuel on board, it's a traditional goodbye
0:31:49 > 0:31:50to the Eritrean chaperones.
0:31:50 > 0:31:53How good is that? We're on our way.
0:32:04 > 0:32:08The team is heading to the waters off the coast of Sudan,
0:32:08 > 0:32:10to a very special site.
0:32:12 > 0:32:14To an underwater village,
0:32:14 > 0:32:17built by Philippe's grandfather, Jacques Cousteau.
0:32:20 > 0:32:23The journey is helped by the seasonal winds
0:32:23 > 0:32:25as they follow an ancient sea passage.
0:32:29 > 0:32:32The Red Sea has always been an important trade route.
0:32:32 > 0:32:38Used by the Egyptians and Romans, it became part of the spice route,
0:32:38 > 0:32:40but that's not all that was traded.
0:32:40 > 0:32:43There's evidence of slaves, for one,
0:32:43 > 0:32:44but tortoiseshell and elephants,
0:32:44 > 0:32:47particularly in the Ptolemaic period.
0:32:47 > 0:32:49Just imagine them building these Hellenistic boats,
0:32:49 > 0:32:52- transporting elephants. - Live elephants?
0:32:52 > 0:32:54Yeah, they were training them to use in their armies.
0:32:54 > 0:32:592,000 years ago there would be a boat passing full of elephants!
0:33:05 > 0:33:08It's halfway through the expedition
0:33:08 > 0:33:12and everyone is exhilarated by what they've discovered,
0:33:12 > 0:33:15but praying on environmentalist Philippe's mind
0:33:15 > 0:33:18is the contrast between the southern Red Sea
0:33:18 > 0:33:19and other oceans he's explored.
0:33:22 > 0:33:25Seeing that balance between really healthy coral,
0:33:25 > 0:33:26very little bleaching,
0:33:26 > 0:33:31no real damage, human damage anyway, but in a way it reminds you that...
0:33:31 > 0:33:35all the other reefs we dive on are in really bad shape because
0:33:35 > 0:33:36this is what they should look like.
0:33:43 > 0:33:46Sudanese waters are also unspoilt and will offer the chance
0:33:46 > 0:33:50to look for rare creatures under threat in other oceans...
0:33:51 > 0:33:54..but getting access has been complicated.
0:33:54 > 0:33:57There's a good buzz at the moment but you've only gotta have
0:33:57 > 0:34:02one official that hasn't been kept in the picture by other authorities
0:34:02 > 0:34:06or some little muddle like that, and we're going to be stuck here
0:34:06 > 0:34:10and once you get stuck in these places, then you're really stuck.
0:34:11 > 0:34:14Next day things take a turn for the worse.
0:34:14 > 0:34:17The seasonal winds have changed direction
0:34:17 > 0:34:18sooner than expected.
0:34:21 > 0:34:22Yeah, it's too bad.
0:34:22 > 0:34:24I mean we've left the Suakin island group
0:34:24 > 0:34:26and we're heading towards Port Sudan now
0:34:26 > 0:34:29but we're being slowed up by this flipping wind.
0:34:29 > 0:34:32The boat's fighting a fierce northerly wind.
0:34:33 > 0:34:37If they don't get to Port Sudan in time to meet the authorities,
0:34:37 > 0:34:39they could be held in port.
0:34:50 > 0:34:54It's another 24 hours of ploughing through choppy seas
0:34:54 > 0:34:57before Port Sudan finally comes into sight.
0:35:01 > 0:35:04We're close enough now. I need to pass the message.
0:35:04 > 0:35:05We've all got to get changed.
0:35:05 > 0:35:08We need long pants out of respect of custom here.
0:35:10 > 0:35:16The Sudanese authorities rarely deal with an expedition of this size.
0:35:16 > 0:35:20The port officials and security want to board immediately.
0:35:20 > 0:35:23The Department of Security has also insisted
0:35:23 > 0:35:25that one of their men remains on board.
0:35:25 > 0:35:30The chap with the dark suit jacket and the cool-looking shades,
0:35:30 > 0:35:32he's got to be our man.
0:35:34 > 0:35:35As-Salamu Alaykum.
0:35:35 > 0:35:37As-Salamu Alaykum.
0:35:39 > 0:35:43While the authorities search the equipment,
0:35:43 > 0:35:46maritime archaeologist Dr Lucy Blue
0:35:46 > 0:35:50is drawn to one of her favourite subjects - shipwrecks.
0:35:50 > 0:35:55- Wreck city up here.- A graveyard. - There's one over there, one here.
0:35:57 > 0:35:59Because of their shallow reefs,
0:35:59 > 0:36:02Sudanese waters are littered with wrecks.
0:36:02 > 0:36:07But Lucy's been researching an Italian cargo ship, the Umbria,
0:36:07 > 0:36:12which was sunk on purpose near the start of the Second World War.
0:36:12 > 0:36:15Her captain wanted to stop the British Navy
0:36:15 > 0:36:18getting its hands on her top-secret cargo.
0:36:18 > 0:36:21It was quite a brave thing to do, really, when you've got,
0:36:21 > 0:36:24you know, a crew of British officers on board,
0:36:24 > 0:36:28actually rifling through your cargo and trying to detain you.
0:36:28 > 0:36:30I'm seeing parallels with the fact that
0:36:30 > 0:36:33we've got customs officials downstairs,
0:36:33 > 0:36:35- rifling through our gear. - That's a good point!
0:36:35 > 0:36:40Oh, these are health. OK, yellow fever, any deaths,
0:36:40 > 0:36:43any mice, rats, any infectious disease.
0:36:43 > 0:36:48OK, well, I'll go through this. OK, sir, see you later. Thank you.
0:36:53 > 0:36:57In World War II, the Red Sea was an important route linking Europe
0:36:57 > 0:36:59with India and other British colonies.
0:37:08 > 0:37:10The day Italy declared war on Britain,
0:37:10 > 0:37:14the captain of the Umbria decided to sink his own ship.
0:37:19 > 0:37:22The vessel itself is listing at about 60 degrees,
0:37:22 > 0:37:26so you get this really distorted impression.
0:37:29 > 0:37:33I don't think I quite appreciated the scale of a 150 metre long ship.
0:37:35 > 0:37:40Lucy wants to investigate the cargo it carried.
0:37:42 > 0:37:46She soon comes across artefacts that hint at life on board.
0:37:46 > 0:37:48Look at this!
0:37:48 > 0:37:51There's thousands of wine bottles
0:37:51 > 0:37:55scattered all over what remains of this hold.
0:37:58 > 0:38:00La dolce vita!
0:38:09 > 0:38:14This is a huge, vast space.
0:38:14 > 0:38:18This must have been the restaurant or the dining area or something.
0:38:20 > 0:38:25And you can still see the stumps from the bottom of the tables.
0:38:25 > 0:38:27It's like entering into the lives
0:38:27 > 0:38:29of the people that were living on board.
0:38:29 > 0:38:31It just looks completely eerie.
0:38:31 > 0:38:34I've just got images of Titanic going through my mind.
0:38:34 > 0:38:38When the Umbria left Italy, the country wasn't yet at war
0:38:38 > 0:38:41so this was officially a neutral cargo ship.
0:38:43 > 0:38:45Oh, yes!
0:38:45 > 0:38:48Three Fiat Lungas.
0:38:48 > 0:38:52There's glass, there's a driver's seat and everything.
0:38:52 > 0:38:55The boat's sitting at an angle
0:38:55 > 0:38:57and they've just fallen down on top of each other.
0:39:01 > 0:39:04But it's not the cars they're here for.
0:39:06 > 0:39:13It's the 5,510 tons of cargo in the next hold.
0:39:19 > 0:39:20This is amazing.
0:39:20 > 0:39:25There are just thousands and thousands of bombs here.
0:39:26 > 0:39:32Just literally surrounded by stack upon stack upon bombs.
0:39:33 > 0:39:39In fact there were 360,000 bombs on board this cargo.
0:39:41 > 0:39:44These aircraft bombs were en route to Eritrea,
0:39:44 > 0:39:47then part of Mussolini's Italian Empire,
0:39:47 > 0:39:50for use against the Allies in East Africa.
0:39:51 > 0:39:54It's easy to understand why the captain didn't want
0:39:54 > 0:39:58the British to get their hands on this deadly cargo.
0:39:58 > 0:40:02To see them laid out like this is just bizarre.
0:40:02 > 0:40:04I know.
0:40:04 > 0:40:08The power, the power of destruction that still remains in this ship
0:40:08 > 0:40:10is a little bit overwhelming.
0:40:13 > 0:40:17Over 600 crates of detonators are stacked separately,
0:40:17 > 0:40:20so these bombs shouldn't explode.
0:40:21 > 0:40:25But if they did, there's enough firepower here
0:40:25 > 0:40:28to destroy half of Port Sudan...
0:40:28 > 0:40:30over 20 miles away.
0:40:36 > 0:40:39The bombs are just overwhelming, they really are incredible.
0:40:39 > 0:40:43They're stacked like eight deep and goodness knows, into the hull,
0:40:43 > 0:40:47how deep they go and it's just, you just think what possesses man
0:40:47 > 0:40:52to want to, you know, just destroy, destroy on that scale.
0:41:00 > 0:41:04The team is due to visit one of the most audacious and extraordinary
0:41:04 > 0:41:06ocean-bed experiments ever attempted.
0:41:08 > 0:41:12It was the brainchild of Philippe's illustrious grandfather,
0:41:12 > 0:41:16Jacques Cousteau, who spent years exploring these reefs.
0:41:17 > 0:41:21The Red Sea has always been an important place in my family's work
0:41:21 > 0:41:24and I've grown up with stories about the adventures that they had.
0:41:24 > 0:41:28I think it's almost like a pilgrimage, coming here for me.
0:41:28 > 0:41:31Kind of gives you an idea of the overall space
0:41:31 > 0:41:34the village, the community, as it existed.
0:41:34 > 0:41:38Captain Jacques Cousteau dreamed up Conshelf II,
0:41:38 > 0:41:42an underwater village built in 1963.
0:41:43 > 0:41:47It was designed to see if humans could live beneath the waves.
0:41:49 > 0:41:54Conshelf II was right off Sha'ab Rumi, which is right up here.
0:41:54 > 0:41:57Yeah, it's quite a ways, actually, away from Port Sudan
0:41:57 > 0:42:00but that was part of the idea.
0:42:00 > 0:42:01It was quite remote.
0:42:01 > 0:42:06It was a time of boundless scientific optimism.
0:42:06 > 0:42:08Astronauts were heading up into space
0:42:08 > 0:42:13and now oceanauts were heading down to the sea floor.
0:42:13 > 0:42:16My father died in 1979, just six months before I was born.
0:42:16 > 0:42:22My grandfather wrote a letter to him and he actually talks about Conshelf.
0:42:22 > 0:42:25"Mon cher Philippe,
0:42:25 > 0:42:31"I will always remember that day of July 1963 when you joined the Conshelf II expedition
0:42:31 > 0:42:33"along the Sha'ab Rumi reef in the Red Sea.
0:42:34 > 0:42:37"The sun was setting but I would not give you time to relax.
0:42:37 > 0:42:40"I was too impatient to show you our village under the sea.
0:42:40 > 0:42:45"Hastily, we both donned our aqualungs and slowly, sensually,
0:42:45 > 0:42:49"we submerged into the welcoming water, as warm as our blood.
0:42:51 > 0:42:54"We started for an unforgettable stroll with slow strokes
0:42:54 > 0:42:56"of our long, stretched legs
0:42:56 > 0:42:58"and breathing deep lungfuls of air."
0:43:16 > 0:43:18This is it.
0:43:19 > 0:43:21This is it.
0:43:23 > 0:43:27God, I can't believe I'm here. I just can't believe it.
0:43:28 > 0:43:33Thinking back to what it must have been like 45 years ago...
0:43:35 > 0:43:39..and kind of envisioning these oceanauts with silver suits,
0:43:39 > 0:43:41this was sci-fi!
0:43:41 > 0:43:44I mean, this was before we landed on the moon.
0:43:44 > 0:43:50This was the first steps of humans living in an alien environment.
0:43:50 > 0:43:54But it has a real sense of being placed here deliberately,
0:43:54 > 0:43:57and that is what's such contrast to what I usually find
0:43:57 > 0:44:03in terms of the remains of human culture or activities underwater
0:44:03 > 0:44:06where they've happened to end up there by default.
0:44:06 > 0:44:10The five divers, oceanauts, lived on the sea-floor for a month.
0:44:10 > 0:44:12I want to see what's inside it, too.
0:44:12 > 0:44:14Yeah.
0:44:14 > 0:44:18Today, this is all that's left of the underwater village,
0:44:18 > 0:44:20the garage for their submarine.
0:44:21 > 0:44:25Wow. How do you actually get in, Philippe?
0:44:25 > 0:44:27Well, there's an entrance over here, I think.
0:44:29 > 0:44:34The submarine would have come up underneath and slowly risen up
0:44:34 > 0:44:38into the area in here, this submarine garage.
0:44:50 > 0:44:52God, I can't believe I'm here.
0:44:55 > 0:44:57No-one really understood the physiological
0:44:57 > 0:45:01or psychological effects of living at pressure.
0:45:02 > 0:45:05Here they were at twice atmospheric pressure.
0:45:05 > 0:45:09Every morning a doctor carried out medical tests.
0:45:09 > 0:45:12We know that cuts and nicks healed faster
0:45:12 > 0:45:15because of the increased pressure
0:45:15 > 0:45:20of the oxygen at depth that caused their body to recover.
0:45:20 > 0:45:25They even had someone come down to give them a haircut every once in a while,
0:45:25 > 0:45:28even though their beards and hair grew slower at depth.
0:45:28 > 0:45:33It was so advanced for its time, wasn't it? It really, really was.
0:45:41 > 0:45:45Fresh food and water were brought down every day.
0:45:45 > 0:45:49But being French, they had wine and champagne,
0:45:49 > 0:45:53which was flat because under pressure the bubbles didn't expand.
0:45:55 > 0:46:01They did some of the first remote video capture of life underwater,
0:46:01 > 0:46:04videoing things that no-one had ever seen before.
0:46:06 > 0:46:09They observed new patterns of behaviour
0:46:09 > 0:46:12and discovered several new species.
0:46:12 > 0:46:14It was really cutting-edge science
0:46:14 > 0:46:18and provided an incredible amount of knowledge for us
0:46:18 > 0:46:21to take another step towards understanding
0:46:21 > 0:46:24the relationship we have with the oceans.
0:46:26 > 0:46:28By the end of the month,
0:46:28 > 0:46:32this bold experiment had proved that man could live underwater,
0:46:32 > 0:46:35although the Space Race was to turn everyone's thoughts
0:46:35 > 0:46:37to a different frontier.
0:46:39 > 0:46:42"I kept your hand in mine to guide you from Starfish House,
0:46:42 > 0:46:44"where oceanauts were having dinner,
0:46:44 > 0:46:48"to the onion-shaped diving saucer garage.
0:46:50 > 0:46:53"Twilight was turning to sheer darkness
0:46:53 > 0:46:56"and our structures became eerie shadows.
0:46:56 > 0:46:59"The fish were just moving pieces of the sea.
0:46:59 > 0:47:03"I was still holding your hand when we returned to the ladder.
0:47:03 > 0:47:06"I felt strangely proud, not of what we had achieved,
0:47:06 > 0:47:09"but because our dreams were always shared so intimately.
0:47:14 > 0:47:17"I saw your shining face, proud to have something to give back to me,
0:47:17 > 0:47:21"and I smiled because I knew that pursuing rainbows in your plane,
0:47:21 > 0:47:23"you would always seek...
0:47:31 > 0:47:33"You would...
0:47:39 > 0:47:42"Because I knew that pursuing rainbows in your plane,
0:47:42 > 0:47:45"you would always seek after the vanishing shapes of a better world."
0:47:59 > 0:48:04After two weeks at sea, the expedition is almost over,
0:48:04 > 0:48:06but there's one final mission.
0:48:06 > 0:48:10In many parts of the world, fishing has dramatically reduced
0:48:10 > 0:48:14the number of sharks, like these scalloped hammerheads.
0:48:14 > 0:48:17That's amazing. Look how many there are!
0:48:17 > 0:48:19I've never seen a school like that.
0:48:19 > 0:48:23Today, it's incredibly rare to see large groups.
0:48:23 > 0:48:25These were filmed over a decade ago.
0:48:26 > 0:48:29We don't know very much at all about hammerheads
0:48:29 > 0:48:32and it's really kind of the luck of the draw these days.
0:48:32 > 0:48:36You know, even in places where you can still find them, it's hard.
0:48:37 > 0:48:41It's so difficult for scientists to get to this part of the world
0:48:41 > 0:48:44that there are no reliable figures on hammerhead numbers.
0:48:44 > 0:48:48So, it's a great chance for Paul to see what he can add.
0:48:48 > 0:48:50Been building up to this for a long time,
0:48:50 > 0:48:53not even just on this part of the expedition
0:48:53 > 0:48:56but I've looked for them before in my life and not found them.
0:48:56 > 0:49:00There is a bit of pressure because it's an important expedition target
0:49:00 > 0:49:03so, really, really, really want to find them.
0:49:03 > 0:49:05See you, buddy!
0:49:05 > 0:49:07There's little fishing in these waters,
0:49:07 > 0:49:10so could this be an important haven
0:49:10 > 0:49:14for fish that are jeopardised elsewhere, like hammerheads?
0:49:15 > 0:49:20Finding a large group might indicate the population here is thriving.
0:49:24 > 0:49:28Paul's heading to the edge of the reef.
0:49:28 > 0:49:31It's just unbelievably pristine, look at it.
0:49:33 > 0:49:35Here currents rise from the deep,
0:49:35 > 0:49:39carrying nutrients which encourage plenty of fish.
0:49:39 > 0:49:41Food for sharks.
0:49:45 > 0:49:49That's good, we've got some grey reef sharks swimming round me now.
0:49:51 > 0:49:53Fabulous things, aren't they?
0:49:53 > 0:49:57It's definitely shark territory.
0:49:57 > 0:50:01Grey reef sharks are agile, curious and often swim in packs.
0:50:03 > 0:50:06Paul needs to be careful not to get too close
0:50:06 > 0:50:08or make any sudden movements.
0:50:12 > 0:50:17While Paul is swimming against the strong currents at 40 metres...
0:50:17 > 0:50:20- Richard!- ..there's a problem developing on the surface.
0:50:20 > 0:50:25- Richard, what's going on? - I have to report we have an emergency situation out here.
0:50:25 > 0:50:28We cannot pick up divers at the moment.
0:50:28 > 0:50:30Engine's down on the Zodiac,
0:50:30 > 0:50:33which means they can't go chasing the divers
0:50:33 > 0:50:37in case there's an emergency because the current's so strong.
0:50:37 > 0:50:40The engine on the rescue boat isn't working.
0:50:40 > 0:50:43The team is worried because Paul is deep underwater,
0:50:43 > 0:50:45swimming against strong currents,
0:50:45 > 0:50:48and if anything goes wrong, there's nothing they can do.
0:50:50 > 0:50:54But Paul is completely unaware of what's going on.
0:50:56 > 0:50:59A single barracuda comes to investigate.
0:51:01 > 0:51:05Above, a ball of them circle in the shallows.
0:51:06 > 0:51:09No-one is sure why they do this
0:51:09 > 0:51:13but they could be herding their prey towards the surface.
0:51:15 > 0:51:16We're at 40 metres.
0:51:16 > 0:51:23It's just wonderful to be in the blue orb of the welcoming Red Sea.
0:51:23 > 0:51:30No hammerheads though. You've just got to happen to be very lucky
0:51:30 > 0:51:32to be in the same place at the same time.
0:51:33 > 0:51:36All right, Richard, we've launched our Zodiac.
0:51:36 > 0:51:40The best we can do is get that boat out to you and swap motors
0:51:40 > 0:51:43so that you've got a working motor on your Zodiac.
0:51:43 > 0:51:46They're on our way, we've done everything we can as fast
0:51:46 > 0:51:47as we could, Richard, over.
0:51:51 > 0:51:55Paul has been swimming against the current for two hours
0:51:55 > 0:51:58when he spots something very rare.
0:51:59 > 0:52:01That's pretty special.
0:52:01 > 0:52:04Can you believe it?
0:52:04 > 0:52:05That's a sailfish.
0:52:07 > 0:52:08Look at him.
0:52:10 > 0:52:12Over a metre long.
0:52:12 > 0:52:13Very rare, that.
0:52:13 > 0:52:18These things are solitary fish and very, very unusual to see here.
0:52:21 > 0:52:24He's got that dorsal spine up.
0:52:24 > 0:52:26That's a sign of aggression.
0:52:28 > 0:52:31Sail fish are the fastest fish in the oceans
0:52:31 > 0:52:34and can reach 68 miles per hour.
0:52:34 > 0:52:38But Paul has still not seen any sign of hammerheads
0:52:38 > 0:52:44and with the boat trouble, the decision is made to halt the dive.
0:52:46 > 0:52:50Had a great dive but no hammerheads.
0:52:51 > 0:52:55We've got some boating things to figure out.
0:52:55 > 0:52:57We don't do boating very well at the moment.
0:53:01 > 0:53:05Really disappointing. At least I did get the hint of sharks.
0:53:05 > 0:53:07It felt like shark water to me,
0:53:07 > 0:53:10and so we're going to do a dawn dive tomorrow.
0:53:10 > 0:53:13This is my mission on this expedition,
0:53:13 > 0:53:16is to learn some more about the hammerheads.
0:53:17 > 0:53:21But was seeing none today a sign that hammerhead numbers
0:53:21 > 0:53:23in the Red Sea are declining?
0:53:28 > 0:53:325am - the last day of the expedition.
0:53:32 > 0:53:37Paul's final chance to look for hammerheads.
0:53:43 > 0:53:45He's heading back to 40 metres.
0:53:47 > 0:53:50Just bursting with life.
0:53:50 > 0:53:53Truly amazing, completely untouched.
0:53:54 > 0:53:59Which is why these waters are in pristine condition.
0:53:59 > 0:54:03Paul passes butterfly fish, feeding on the coral.
0:54:06 > 0:54:08Almost one in five fish species found here
0:54:08 > 0:54:11lives nowhere else on earth.
0:54:15 > 0:54:20Suddenly, a rare silky shark comes close.
0:54:20 > 0:54:23Recognisable because of its shiny skin,
0:54:23 > 0:54:26it can grow to over three metres long.
0:54:36 > 0:54:40Paul has been drifting along the edge of the reef for nearly an hour.
0:54:46 > 0:54:49Then, something moves in the distance.
0:54:51 > 0:54:53There you go.
0:54:54 > 0:54:58A school of hammerheads, there's about 30 of them.
0:55:03 > 0:55:05Look at that!
0:55:05 > 0:55:08We've just seen one of the rarest sights on earth,
0:55:08 > 0:55:11a school of hammerheads flying through here.
0:55:15 > 0:55:18It's a distant sighting but still exceptional
0:55:18 > 0:55:20to see them in such a big group,
0:55:20 > 0:55:24and a very good sign for their population here.
0:55:33 > 0:55:35What a gift.
0:55:35 > 0:55:37Thank you, the Red Sea!
0:55:48 > 0:55:51He saw them, he's giving the double thumbs-up.
0:55:51 > 0:55:53He's giving the double fins!
0:55:55 > 0:55:59Perseverance! You prevailed!
0:55:59 > 0:56:02We've got to stop doing this last minute stuff,
0:56:02 > 0:56:05- it's going to kill us!- Fantastic. - It really was great.
0:56:05 > 0:56:08- Good for you, man. - There was about 30-odd of them.
0:56:08 > 0:56:10- 30!- 30!
0:56:10 > 0:56:13In many other oceans, a sighting like this
0:56:13 > 0:56:17would be a thing of the past because of over-fishing.
0:56:17 > 0:56:22It's another reminder that this part of the Red Sea is unique.
0:56:22 > 0:56:25I've done over 6,000 dives but it was truly a marvel.
0:56:25 > 0:56:28I have been looking for hammerheads for most of my diving life.
0:56:28 > 0:56:31There's just something about them and I've never seen any.
0:56:31 > 0:56:35A school of hammerheads flying through here.
0:56:35 > 0:56:39Just by witnessing it, recording our experiences,
0:56:39 > 0:56:43we have added to the science database here in the southern part
0:56:43 > 0:56:45of the Red Sea because so little has been done.
0:56:49 > 0:56:52It's a fantastic end to an expedition which has shown
0:56:52 > 0:56:56just how important this small sea is.
0:57:03 > 0:57:07The southern Red Sea gives you some indication of what the seas
0:57:07 > 0:57:10used to be like and if we're lucky, what they could be like again
0:57:10 > 0:57:12in the future if they're managed properly
0:57:12 > 0:57:15and we give them a little bit more respect.
0:57:15 > 0:57:21We are leaving this place richer in ourselves, richer in our knowledge
0:57:21 > 0:57:26but there's so much that it holds that we don't understand,
0:57:26 > 0:57:28and that's so exciting.
0:57:30 > 0:57:34I came up from every dive I've done in Eritrea just feeling
0:57:34 > 0:57:38really, really positive, and I don't think I've had that sensation
0:57:38 > 0:57:40anywhere else in the world.
0:57:43 > 0:57:48What we've learnt in the Red Sea is that oceans can survive.
0:57:48 > 0:57:52It sounds odd but oceans are fragile and yet they can survive.
0:57:56 > 0:58:00Next time, the team explores the vast Atlantic.
0:58:00 > 0:58:05They'll brave the toxic world of our ancient oceans.
0:58:05 > 0:58:08We are three and a half billion years back in time.
0:58:08 > 0:58:12They'll investigate the invasion of a deadly species.
0:58:13 > 0:58:17And try to protect a fearsome predator.
0:58:17 > 0:58:20Sharks everywhere!
0:58:27 > 0:58:30Subtitles by Red Bee Media Ltd
0:58:30 > 0:58:33E-mail subtitling@bbc.co.uk