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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.
00:17But the secrets of our oceans have remained largely undiscovered.
00:23I win! I think so.
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
00:52and 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.
01:20The team is about to explore the mighty Atlantic.
01:26This vast sea is the second-largest of the world's oceans.
01:33It dominates the Western Hemisphere
01:36and covers a fifth of the planet's surface
01:3941 million square miles.
01:43Its northern boundary is the Arctic
01:45and its southern boundary is the Antarctic.
01:48To the west you've got the whole Americas
01:50and to the east, of course, you've got Africa and Northern Europe.
01:53So, I mean, it's the same extremes.
02:00It's the youngest of the great oceans
02:03but one of the most influential
02:05with an enormous impact on our climate.
02:10The Atlantic is a critical ocean
02:12not just because it's such a beautiful, vast and varied place
02:16but because it's so important for the health of the planet.
02:20But it's now under threat.
02:22Increasing commercialisation of its rich resources
02:25is changing it dramatically.
02:30The Atlantic is more than I think many people realise.
02:33It's being lost before we even, I think, grasp its full significance.
02:40The team is here to investigate
02:42how man is endangering our crucial relationship with this ocean.
02:50We are three-and-a-half billion years back in time.
02:56Toonie Marto is a marine biologist and oceanographer.
03:05On this expedition, she'll brave the alien world of our prehistoric seas.
03:12It's dark and glaring and just very lifeless by the looks of things.
03:20Maritime archaeologist Dr Lucy Blue
03:23will investigate how conquering the Atlantic helped change our history.
03:29It's clearly a hugely important highway in terms of connecting continents
03:33but also in terms of the early seafaring activities
03:37in this particular part of the Atlantic Ocean.
03:42And environmentalist Philippe Cousteau, grandson of ocean pioneer Jacques Cousteau,
03:47will examine how we are threatening the future of this ocean.
03:52It's like seeing a polar bear on the plains of Africa.
03:55It just doesn't belong here.
03:58And he'll become human bait in an experiment to protect a top predator.
04:03Sharks everywhere!
04:09The team has come to the heart of the Atlantic Ocean,
04:12to the tropical waters of the Bahamas.
04:18Here there are unique marine environments
04:20which can reveal this ocean's past and its complex future.
04:31For their first mission, the team is planning to explore one
04:35to discover what our planet's earliest oceans were like.
04:47Let's go.
04:57They're heading to a strange marine environment,
05:00one of the only places in the world where dark, toxic waters mimic the Earth's first oceans.
05:08There it is, Tony.
05:12It's called the Black Hole.
05:14This could well be the most dangerous dive we're going to make.
05:18It looks like a giant pupil looking up at us.
05:22Formed by chemical erosion over many thousands of years,
05:26this isolated black hole has developed conditions
05:30similar to the seas of three and a half billion years ago.
05:35The team wants to find out what those early seas were really like
05:39by diving deep into these waters.
05:43There's only ever been three scientific expeditions here,
05:46so this is a great opportunity to actually get in the water
05:50and try and glean more understanding about this almost isolated environment.
05:57Though it's relatively unexplored,
05:59there's one thing scientists do know about this deep-water pool
06:02that, like our early oceans, parts of it are toxic and dangerous.
06:08I understand there's a layer down there.
06:11And this layer is kind of suspended around about 20 metres.
06:15It's a metre deep.
06:16And in that layer is very high concentrations of poison, hydrogen sulphide.
06:21And I'm going to try and find out what's going on down there.
06:24That layer is very high concentrations of poison, hydrogen sulphide.
06:29And under that, I have no idea what to expect whatsoever.
06:33Lucy and Philippe will be at the surface,
06:36taking temperature and oxygen readings
06:38to monitor the conditions as Tooney and Paul descend.
06:44We're going to drop the sensor down with the divers
06:47and kind of record on the way down
06:49so we can get an idea, hopefully, of what's going on down there.
06:54It's a deep dive into toxic chemicals.
06:58Dive safety supervisor Richard Bull is worried.
07:02Quite frankly, I'm a bit twitchy about it, all right?
07:05Don't forget you can bail out at any point.
07:08If you're a bit twitchy, get out of bed.
07:10It's better to be stood up here wishing you were in there
07:13than in there wishing you were stood up here, all right?
07:16Tooney and Paul, you're looking out for each other.
07:19You are each other's standby, all right?
07:21I'm not sure it's going to be that pleasant down there,
07:24and if it's not that pleasant, I want my wingman on standby.
07:27I'm yours. Don't worry.
07:29Three points to fish. OK.
07:31Two, one...
07:42Man, that really is looking over the precipice, isn't it?
07:47We're just suspended perfectly.
07:49Over this huge black hole, and it feels as if it's drawing us down.
07:56Paul and Tooney plan to spend longer in the black hole
07:59than anyone has before.
08:01No-one can be absolutely certain what the effects will be.
08:07Tooney, here's the science kit coming down.
08:11How deep are you right now?
08:13Yeah, we are now at 15 metres, Philly.
08:17They keep going down.
08:20So far, the dive has been completely normal.
08:24But then they reach 18 metres.
08:26Wow, Philly, the temperature's just soared by six degrees.
08:31Yeah, Philly, my head feels quite normal,
08:36but my legs are really, really hot,
08:39and I'm in some kind of strange lair.
08:42What are you showing up there for temperature?
08:45It's just zipped up to about 30 degrees C.
08:48We're reading some interesting figures here on the probe.
08:52It seems that the temperature has spiked quite considerably.
08:56It's just in a metre.
08:58That's amazing.
08:59Usually, the deeper you go, the colder it gets.
09:01This is incredible.
09:03God, I've never even heard of anything like that before.
09:05No, no, nor have I.
09:07To find out what's causing the sudden rise in temperature,
09:10they descend even further.
09:14Oh, my goodness, it's purple.
09:17This is bizarre.
09:23That is psychedelically purple.
09:26It's like being in an outer-space chemical soup.
09:30As a marine biologist,
09:32Tooney recognises what the purple cloud must be.
09:36We're right in the middle of a layer of purple sulphur bacteria.
09:43They contain a pigment which they use to attract sunlight,
09:47and that pigment is purple.
09:50The bacteria absorb the sunlight's energy to photosynthesise.
09:54But not all the energy is absorbed.
09:59And the reason it's warm is because purple sulphur bacteria
10:02are not particularly good at trapping that sunlight.
10:06So about 70% of the energy of the sun is just dissipated.
10:11And that's what's causing the sudden rise in temperature.
10:16So about 70% of the energy of the sun is just dissipated as heat.
10:23Bacteria like these were one of the few life-forms
10:26that could survive in our early seas.
10:29But when they photosynthesise,
10:32some produce a poisonous by-product, hydrogen sulphide.
10:37In high concentrations, that's as deadly as cyanide.
10:46Oh, God, I can smell it in my face mask.
10:50Oh, it really smells.
10:53None of their face is exposed to the water.
10:56What's happening is that their skin is actually absorbing the hydrogen sulphide,
11:00and that's moving its way and circulating through their body into their sinuses,
11:04and that's how they're smelling it.
11:06To discover more about conditions in our early oceans,
11:10Paul and Toonie need to find out what's below this toxic layer.
11:15It can't possibly get any worse.
11:17Let's go down another half a metre or so.
11:24Oh, man!
11:26It's absolutely pitch black.
11:29It's like somebody's just sucked all the light away.
11:32And the bacteria just above us have actually sucked all the light out.
11:37So no sunlight energy reaches this layer.
11:41This is why the black hole appears so dark from the surface.
11:46Then Lucy discovers something else.
11:50The oxygen levels have gone from 7.8 at the surface all the way down to 0.18.
11:56Wow.
11:57I know, that's...
11:58Paul, Toonie, surface, we're also noticing on the probes
12:01that the oxygen level has dropped considerably.
12:07There's almost no oxygen in the water here.
12:11The layer of bacteria acts as a barrier,
12:14preventing the sunlight and oxygenated water above from getting down here.
12:22These are the conditions they have been looking for.
12:27What Paul and I are swimming through is what the oceans would have once been like.
12:32Dark and gloomy.
12:34Very, very little oxygen and just very lifeless by the looks of things.
12:42With its high concentration of sulphur bacteria and no light or oxygen,
12:47this body of water is as close as we can now get to our ancient oceans.
12:56We are three and a half billion years back in time.
13:00The oceans formed when the Earth was about 200 million years old.
13:06They were a series of hot, oxygen-free pools with very little life,
13:11dotted across the barren volcanic landscape.
13:15They remained that way for over a billion years.
13:20I'm getting some weird sensations on my skin.
13:24It's really, really tingling.
13:26After just 20 minutes, their bodies have started to react to this harsh environment.
13:32It's having some weird effect on our skin.
13:37I can always feel my hair burning.
13:40I need to get this suit off because I'm itching in here.
13:43These chemicals really make me itch.
13:50Dive safety supervisor Richard Smith says
13:54Dive safety supervisor Richard Bull has heard enough.
13:57It's time to get them out.
14:00Too much we don't know about.
14:02We don't know how the gas affects them.
14:05We don't know how it affects equipment.
14:07Just so many ifs and buts.
14:21How was it?
14:23Everything about it is weird.
14:25It's getting warmer and warmer and warmer.
14:27As you go deeper, huh?
14:28To the point of it being oddly, unhealthily warm.
14:32Look at that.
14:33That's where the metal's been oxidised by the bacteria.
14:37This is a brass clip and this is a brass-bodied pressure gauge.
14:40I just noticed they've both gone off.
14:43But it's no surprise to see some other manifestation of that chemical reaction.
14:49It's pretty powerful.
14:53That's how our oceans were.
14:55Not these wonderful live masses of water covering 70% of our surface.
15:01They were like that weird place.
15:03That's where we started.
15:04And so it's fantastic to be in a bit of water
15:08that is exactly the same as our oceans were 3.5 billion years ago.
15:12I mean, top that.
15:23The Atlantic Ocean
15:28Since then, the Atlantic and all our oceans have changed beyond recognition.
15:35The rich life of our modern oceans is a vital resource for man
15:39and has been for hundreds of thousands of years.
15:43But today, we're increasingly threatening.
15:49OK, well, it's whiteboard.
15:51OK, everyone, so we've got it sussed here.
15:53An easy trip...
15:55Philippe is going to investigate a growing problem
15:58that is changing the balance of life here.
16:01An alien species brought to this ocean by man.
16:10Invasive species are having a devastating effect
16:13on more and more of our oceans.
16:18In this part of the Atlantic,
16:20here is the lionfish.
16:24Probably one of the top five environmental crises
16:27we're facing today is invasive species.
16:29And lionfish is really the poster child of that
16:32here in the Atlantic Ocean.
16:34I love diving with lionfish, you know?
16:37I've done it many times in the Pacific Ocean,
16:39where they belong, not in the Atlantic,
16:41not here in the Bahamas.
16:445...
16:464...
16:483...
16:492...
16:501...
16:56Philippe wants to discover how the lionfish
16:59could be affecting the Atlantic Ocean.
17:04Native to the warm waters of the Pacific and Indian Oceans,
17:08lionfish live mainly around coral reefs.
17:14MUSIC PLAYS
17:24Wait! Loose!
17:26Have you got one?
17:28Right here!
17:31It's like seeing a polar bear on the plains of Africa.
17:34It just doesn't belong here.
17:39The fish are popular in aquariums,
17:42so scientists suspect that unwanted pets
17:45may have been released by their owners into Atlantic waters.
17:50The first sightings began about 20 years ago.
17:53Here's one here, look!
17:55They are clearly doing very, very well.
17:58You can see this other one right up here,
18:00just sitting on the ledge.
18:02They're everywhere. It's unbelievable.
18:05Smarter than anything else.
18:08These ornate fish
18:10are one of the ocean's most poisonous creatures.
18:13They have spines on their fins.
18:16At the base of these spines are venom glands
18:19containing a neurotoxin.
18:21When the spine punctures a victim,
18:24the toxin is released.
18:27Old wives tales would say
18:30that fishermen who would grab lionfish
18:33and try to pull them out of their nets
18:36would get stung
18:39and they would throw themselves overboard and commit suicide
18:42because the pain was so excruciating.
18:52But the venomous spines aren't the real danger here.
18:56So far on this dive,
18:58the lionfish is the only relatively large fish
19:01that Philippe and Lucie have seen.
19:04These invaders are skilled and efficient hunters
19:07that decimate the native fish population.
19:11Wow, he's eyeballing something.
19:13He's just kind of sneaking up on it.
19:15Whoa! Did you see that?
19:17He just went after something.
19:19Oh, yeah.
19:21Wow. That is so rare.
19:23Typically lionfish are nocturnal feeders
19:26and for him to have done that
19:28just shows just how voracious and deadly
19:32these creatures are.
19:38And because they're new here,
19:40the native fish don't yet recognise them as predators.
19:44All the little fish swimming around it,
19:46they're just hanging out there.
19:48So the idea of identifying it as a predator,
19:52they haven't acknowledged that just yet.
19:54Look at them, they're almost following it at the moment.
19:58Lionfish target young fish, which are easily caught.
20:03The native fish population is in danger of being wiped out.
20:08That was the problem in action.
20:11This is bad news for the health of this ecosystem.
20:14Bad news for potentially important fish,
20:17for the other creatures that live here
20:19that are part of the natural order of this food chain.
20:24And it's getting worse.
20:26Lionfish have few natural predators in the Atlantic,
20:29so their population is exploding.
20:33From just a handful 20 years ago,
20:35there are now countless lionfish,
20:38and they've spread from the Caribbean
20:40as far north as Rhode Island.
20:48For me, it was just the way that the other fish
20:50were just sort of hanging out around them,
20:53as if they had no fear or any indication
20:56that they were their predators.
20:58They were everywhere.
21:00I was looking for grouper, I was looking for parrotfish,
21:02just keeping my eye out for things that should be here,
21:05and I didn't see any of them in the abundancy
21:08that I saw lionfish.
21:09That's very worrying.
21:11I don't think there's anything we can do about it.
21:13I really don't.
21:14Except for try and learn,
21:16so that if it happens again with another species,
21:19we're a little more prepared to deal with it.
21:21I think that's about all we can hope for, which isn't much.
21:30There's no sign of this Atlantic invasion stopping,
21:33and it's far from the only example of man's impact on this ocean.
21:39Later in the expedition,
21:41the team will dive with sharks to protect these top predators,
21:45victims of increased commercial fishing here.
21:52These waters are being changed by man,
21:55but they brought the first settlers to these islands
21:58over 1,300 years ago.
22:03Good luck in the Lucayans, guys. I don't want to see any...
22:06There are archaeological discoveries to be made
22:09in terms of that whole sort of migration
22:12of people out of South America
22:14and slow colonisation of various islands in the Caribbean,
22:18and this part of the Atlantic Ocean.
22:27Today, maritime archaeologist Dr Lucy Blue is travelling inland
22:32in search of the lost civilisation of the Lucayans.
22:39The Lucayans were an ancient people
22:41who travelled here from South America on wooden rafts.
22:45Using the ocean currents and prevailing winds.
22:54Lucy will be the first archaeologist to investigate a sea cave
22:58thought to be a Lucayan burial site.
23:03This is the first time in 20 years or so
23:05that anybody's been allowed to go back and have a look
23:08and see if, indeed, anything still remains there.
23:12Very little is left of the Lucayans' ancient civilisation.
23:16Could this cave hold evidence of their rich history?
23:21It's a watery state. It's really quite atmospheric.
23:24Quite peaceful, actually, isn't it?
23:26Sort of fitting that you bury your dead there, in a way.
23:33Hopefully, my expertise will allow me
23:37Hopefully, my expertise in the archaeological remains
23:40will add something to an understanding.
23:42Assuming there's anything there, though,
23:44we're still not entirely sure that we're actually going to find anything.
24:00And into the depths we descend.
24:07Oh, that is just like the hand of God touching the cavern.
24:13Finding anything won't be easy.
24:16This underground labyrinth of caverns extends for many miles
24:20and eventually joins the ocean.
24:28The limestone structure of the Bahamas,
24:31being so porous and fragile,
24:34creates these vast cave systems.
24:38The Lucayans' creation legend tells how they were trapped in a watery cave
24:43until the sun and the moon freed them.
24:50So caves were sacred places and used for burial.
24:59What about there?
25:02Ah! Look at this!
25:07That's really eerie.
25:15Deep within the cave, Lucy spots something remarkable.
25:20Titty-titty, come in, come in.
25:24Come on.
25:27God, it's incredible to think this could have been here
25:31for over 1,400 years.
25:34It's lying here in its watery grave.
25:42I can't see any other sort of burial artefacts with it,
25:46no bits of pottery, but fortunately we can't get too close.
25:49I might just get a little bit closer, though.
25:53But is this skull Lucayan?
25:56One feature would prove it.
26:00Apparently, they used to strap planks of wood on the skull
26:04and this would give it a very pronounced shape.
26:07It was supposed to be a sign of, you know, beauty.
26:11It's a bit like, you know, when the Japanese bind their kids' feet.
26:14It's the same sort of effect.
26:16Actually, it does look like it's had that on its head.
26:23The characteristic flat forehead
26:26shows this really is the skull of a Lucayan.
26:34It's thought the bodies were dropped into the caves from openings above.
26:38But to Lucy, the position of the body suggests another possibility.
26:44The Lucayans themselves were actually really competent freedivers
26:48and so they could have actually carried the body
26:51and placed it in this position.
26:54To me, it looks very deliberately placed.
27:01But while the Atlantic transported the Lucayan settlers here,
27:05it also brought about their demise.
27:08When, hundreds of years later,
27:10other races migrated across this ocean...
27:13The Lucayan people lived here quite peacefully
27:16until the Europeans arrived, Columbus and his men.
27:20They took a population of roughly 60,000 people and enslaved them.
27:25And if they refused to be enslaved, then they shot them.
27:28After Spanish colonisation,
27:30European diseases and mass suicides in response to slavery took their toll.
27:35Within a generation, the Lucayan peoples no longer existed.
27:45I felt very privileged looking at some of these people
27:48and seeing how they were able to survive.
27:51They were able to survive.
27:53They were able to survive.
27:56I felt very privileged looking at somebody in their final resting place.
28:01When you find, you know, the remains of people that lived,
28:05you know, sort of 1,400 years ago or something...
28:08A vanished civilisation.
28:10Yeah, that makes it very special.
28:17Today, the Atlantic still has a great influence on our lives.
28:22For hundreds of years, this ocean was central
28:25to the discovery of new worlds and colonial expansion.
28:31It's clearly a hugely important highway in terms of connecting continents,
28:35but also in terms of the early seafaring activities
28:39in this particular part of the Atlantic Ocean.
28:45This ocean has been especially important
28:48in shaping the history of Britain and the United States,
28:51bringing settlers, trade, even war.
28:59Lucy wants to investigate a battle between Britain and America
29:03by identifying a significant shipwreck,
29:06one that might be the HMS Southampton.
29:09There are so many incidences of shipwrecks in this area.
29:12I mean, the Bahamas, in Spanish, means shallow waters.
29:15The war was a dispute over Atlantic trade routes
29:19between England and America in 1812,
29:22shortly after the War of Independence.
29:27A shipwreck has been found on a reef near Conception Island.
29:32It's not been mapped at all, it's not been surveyed extensively,
29:35it certainly hasn't been excavated,
29:37so, you know, it hasn't really been investigated.
29:42Lucy wants to find out if this wreck is the HMS Southampton.
29:49She wasn't actually that big, she was only about 120-odd feet,
29:52carrying 32 guns.
29:53Wow, that's a lot of guns for 120 feet.
29:55I know, and a crew of nearly 200 or something.
29:57It must have been actually quite cramped.
29:59Awfully close.
30:00And they spent a lot of time at sea back then.
30:02I know, totally.
30:03It'll be interesting to see if that complement of guns and anchors
30:07and everything actually are reflected on the seabed.
30:14But the weather may scupper their plans.
30:20Well...
30:24We should be prepared for some kind of jiggery-pokery with the schedule
30:27or maybe not even making it, I don't know.
30:29Oh, really?
30:30Yeah, they're talking, you know, gale force.
30:32Really? Yeah.
30:34So...
30:35And how long is that likely to last?
30:37We don't even need gale force.
30:39If it's on the edge of 20 knots,
30:41it'll be on the edge of our diving capability.
30:45The weather moves in, and conditions deteriorate rapidly.
30:53This is just not what we want at all.
30:57And as ever, it's a tight schedule, so if we don't get a move on...
31:04As well as the shipwreck,
31:06they also need to fit in a challenging dive with the gale force.
31:10As well as the shipwreck,
31:11they also need to fit in a challenging dive with sharks.
31:15So they decide to press on.
31:19After hours of forging through choppy seas,
31:22they finally get near the shipwreck.
31:31It's not getting any better.
31:32The boat's rocking and it's blowing like crazy,
31:35so it's not making our job any easier.
31:38With the wind, the current and this position,
31:40it's a bit marginal, really.
31:50In these conditions,
31:51it's easy to see how a ship could founder on this reef.
32:00Now Lucy can finally try to discover whether it is the Southampton.
32:08So there's an anticipation,
32:09but also you just don't know what you're going to find, do you?
32:13So that's...
32:15That's quite exciting, really.
32:25Several metres down, conditions are much better.
32:30So Lucy and Philippe start their detective work.
32:33So I'm just trying to find out any clues of...
32:37..the wrecking of the ship.
32:38I'm just trying to see if I can find any of the cannon or the anchor.
32:48Aha! Look!
32:49Philippe, Philippe, Philippe!
32:52Look at that!
32:53Look, look, you can see one, two...
32:56There's loads of cannon all over the place.
33:00Any exposed wood will long have rotted away,
33:03but there are artefacts spread over a wide area.
33:07Once you've trained your eyes, there are cannon everywhere.
33:11Another one over there.
33:13They're just lying here.
33:15Look, there's another one here.
33:18I've never seen so many cannon
33:20in such a concentrated area on a ship before.
33:23I mean, just look at the size of this thing!
33:27I mean, it's about as long as I am!
33:31But are these cannons from the Southampton?
33:34The Southampton had 32 guns.
33:36There were 26 of these 12-pounders.
33:39I think this is a 12-pounder. We need to measure it.
33:43The 12-pound guns on the HMS Southampton
33:46were used by the HMS Southampton.
33:50The 12-pound guns on the HMS Southampton
33:53were said to be between six and a half and seven feet long.
33:59That's six foot seven.
34:02So this is the right kind of cannon, then, Lucy?
34:05I think so. I think so.
34:09Ah! The other thing that's quite distinguishing about this
34:13is that the 12-pounders of this era
34:17had these little sort of rings attached to their ends,
34:21which was quite unusual.
34:23Not many of the cannons had these,
34:25so that looks like one of the types of cannon
34:28that the vessel would have been originally consigned with.
34:32The cannons alone aren't enough for a positive identification.
34:36Lucy needs to find more evidence.
34:43Look, look, look! It's huge!
34:45This is just incredible.
34:47You can see this anchor just sitting here.
34:51It's a British anchor.
34:53You can see because of the V-shaped arms at the bottom of the anchor.
34:56This is very distinctive of British naval vessel anchors.
35:00If it was from an American vessel,
35:02it would have been more rounded at the base.
35:05It's just another clue, in a way,
35:07as to understanding if this is the wreck of the HMS Southampton.
35:16I would have expected maybe to find a pile of chain or something
35:20attached to the anchor.
35:22That would have been iron that should still be here.
35:24No, no, no, not for this period,
35:26because they would have been using ropes
35:28rather than chain to actually haul the anchor.
35:35She probably would have thrown these anchors aground
35:38as she wrecked here during the night.
35:41By the morning, they realised that there was no saving the vessel
35:45and they had to abandon ship.
35:47So, again, another clue confirming this is the HMS Southampton.
35:53The size of the cannons,
35:55along with the type and position of the anchors,
35:58have convinced Lucy this is the HMS Southampton.
36:02It's a record of the November night in 1812
36:05when towing a captured American ship to Jamaica
36:08she hit this reef and sank.
36:15It brings to life an event and a particular battle
36:18that has been forgotten a lot in our histories,
36:21both the UK and American.
36:26The war was finally resolved with a treaty signed in 1814.
36:30Neither side was victorious.
36:32But it confirmed the status of the war.
36:36You know what this impresses upon me?
36:38I mean, the Atlantic played a huge role in that war alone,
36:42not to mention many, many others.
36:45Such a vast, critical ocean.
36:49It is like a snapshot in time,
36:51which basically the ocean has preserved
36:53for us to come and investigate.
36:55And so, in a way, it's like a snapshot in time
36:58of what's going on in the Atlantic.
37:00It's like a snapshot in time
37:02preserved for us to come and investigate.
37:04And so, in a way, the ocean actually holds a story,
37:07which we are very unlikely to find in any other context.
37:15The Atlantic has helped shape our distant and more recent past.
37:19Now the expedition is heading north-west
37:22to investigate its future.
37:27We're heading for North Bimini, aren't we?
37:29Yeah, we're going to come off the banks.
37:31We're going to get down here and drop the anchor overnight.
37:37The future of the Atlantic is being shaped by man.
37:41The effects of large-scale commercial fishing
37:44are damaging this mighty ocean.
37:46In the last decade, some fish stocks have fallen by 95%.
37:52One fish is particularly hard hit.
37:55The shark.
37:57How many do we catch every year?
38:01Human beings catch between 70 and 100 million sharks every year.
38:0870 to 100 million sharks a year.
38:13Some sharks are caught for their fins, used in shark fin soup.
38:18But millions of sharks are bycatch,
38:21caught unintentionally by big commercial fishing operations.
38:25Sharks are so critical.
38:27They are the apex predator.
38:29They help to weed out the sick and the diseased
38:31and make sure that the fisheries and the food chain beneath them
38:34is healthy and viable.
38:36And when they remove sharks from that chain,
38:40it has just disastrous effects on the entire ecosystem.
38:46So the team is going to dive with sharks
38:49to investigate a pioneering technique,
38:52a shark repellent that could help protect these vital creatures.
39:00Coming up slowly. It's a small one.
39:03Belief and Toony are going to team up with scientists
39:06from the shark lab at the Bimini Biological Field Station.
39:10For the last 25 years,
39:12they've been monitoring the population here,
39:15catching and then releasing the sharks
39:17once they've collected their data.
39:20There was a shark caught on one of the hooks.
39:23I mean, it's giving a good thrash in the water
39:25so it's still alive and obvious.
39:27To track the diminishing population,
39:29they need to attach an identity tag to this shark.
39:33Belief is going to monitor the process underwater.
39:37We've got to be very, very careful.
39:39It's going to be an upset shark.
39:41And it's happened before that they can break free from the line.
39:44So we're going to give it a lot of space,
39:46a lot of birth and a lot of respect.
39:49Looks like a tiger shark.
39:51That is a tiger shark, all right.
39:54Tiger sharks are known to be
39:56one of the more dangerous sharks in the world.
39:58I normally would never get this close to a tiger shark.
40:01We've got to be very, very careful.
40:03It's going to be an upset shark.
40:05And it's happened before that they can break free from the line.
40:08So we're going to give it a lot of space,
40:10a lot of birth and a lot of respect.
40:19Watch out!
40:28Whoa!
40:32There's a close call there.
40:34That's why you've got to be really careful.
40:38So we're doing a data tag, basically.
40:43As sharks become more threatened,
40:45tags can help identify when and where they're being fished.
40:49Do you want to push it in?
40:51Are you going? Pull the wood out.
40:53There you go, and the tag stays in, you see.
40:56This shark has been caught deliberately for research,
40:59but commercial fisheries catch countless sharks unintentionally.
41:04Long lines are set up by commercial fishermen
41:07miles and miles and miles long
41:09with thousands of hooks laid along them.
41:11Sharks are often left for a long period on those lines
41:14and they die.
41:27She wanted to give me a little goodbye present.
41:31And off she goes. She looks good.
41:35Millions of these predators are caught on commercial lines.
41:39So the hunt is on for an effective way of preventing sharks
41:43from getting trapped on them.
42:00Paul and Lucy have joined scientists
42:02who've developed a material they believe will repel sharks.
42:07This is the very stuff right here. It's an alloy, a mixture of metals.
42:12The hope is that hooks made of the repelling metal
42:15could be used on long line fishing hooks
42:18so fewer sharks end up as bycatch.
42:23The metal is electropositive.
42:25It produces a charge that's conducted by salty water.
42:28Well done.
42:30OK, just let him settle down a bit.
42:32So I'll grab him, OK?
42:35Lucy and Paul are going to test the metal on a juvenile lemon shark.
42:39Lucy has been shown a handling technique to help the experiment,
42:43putting the shark in a coma-like state.
42:46I'm going to try and basically turn him on his back,
42:49so we've got to try and move him over.
42:53Be ready for him. Steady as you go.
42:59Well done.
43:02When the tail becomes immobile, basically when she's not moving at all...
43:07OK, so she's totally out of it at the moment.
43:13In this state, the shark is very unresponsive.
43:17Paul's going to bring a small piece of the metal close to its head.
43:28Are you ready, Lucy?
43:31Time to see if the shark will react to the metal.
43:46OK.
43:49OK, it works.
43:51I think that's definitely a conclusive experiment.
43:55So it works.
43:58Even in a comatose state, the shark sensed the metal and was repelled by it.
44:03So if you've got a set of great fishhooks made out of this stuff,
44:06you can do selective fishing.
44:08You're going to get more of what you do want to catch
44:11and less, or hopefully none, of what you don't want to catch.
44:16The expedition is coming to a close.
44:20But there's one final shark mission for Toonie and Philippe.
44:28CHUM
44:35Chum, a mixture of mashed-up dead fish, has been spread in the water.
44:40It's attracted blacktip and Caribbean reef sharks.
44:44Oh, we've got sharks.
44:46There's some sharks out here.
44:48You can see their fin tips just going around the water.
44:52CHUM
44:56They're going to test another shark repellent,
44:59a liquid that could be attached in time-release pouches to long lines.
45:06To make the conditions for the experiment authentic,
45:09it's got to be carried out in open water,
45:12teeming with adult sharks.
45:16Philippe and Toonie will dive in amongst the sharks
45:19and release the repellent by hand.
45:25There are some big sharks down there, actually.
45:27They're a good couple of metres,
45:29which I don't think I was quite expecting.
45:31I was expecting slightly smaller sharks, to be honest.
45:36Caribbean reef and blacktip aren't the most aggressive of sharks,
45:40but the chumming has attracted quite a few.
45:43One, two, three, four, five, six...
45:47..and the small one at the back is seven.
45:51That's bizarre. That makes my heart go a bit funny.
45:55It's quite a bizarre sensation to be sitting on the side of a boat
45:58about to drop backwards into a pool of teeming with sharks.
46:04Safety divers and first aiders are standing by.
46:17Oh! Oh, my goodness!
46:21Sharks everywhere.
46:23All around us.
46:26It's just incredible.
46:30Oh, God, it's having a good look at me.
46:33Whoa!
46:35Oh, yeah! That was close. That was close.
46:38Nice! That was close.
46:43Shark chaos!
46:46More and more sharks are gathering.
46:49This should be the stuff that really scares them off.
46:52It's a sensation.
46:54It's a sensation.
46:56It's a sensation.
46:58It's a sensation.
47:00It scares them off.
47:02It's essentially distilled tissue from sharks, from dead sharks.
47:09Scientists realised sharks are driven away by the smell of rotting shark.
47:16As you can see, they're kind of circling us a lot right now.
47:19You can see them getting a little bit ticked off at each other.
47:24A little bit aggressive towards each other.
47:28Philippe and Tuni decide to release the repellent.
47:33This is the first time that this repellent has been tested like this.
47:37This isn't a game. This is serious business.
47:49Sharks have a very acute sense of smell,
47:52but it takes a few minutes for the liquid to disperse.
47:58One by one, the sharks leave.
48:02They keep swimming further and further away from us.
48:07Clearly, they didn't like something.
48:10All the other fish are still here.
48:13But the sharks have disappeared.
48:18There are not so much signs of coming back either.
48:22The experiment's been a complete success
48:25and could play a vital role in protecting sharks in all our oceans.
48:33Fantastic!
48:35The sharks kind of do an in-sense of something and out again.
48:39Yeah, definitely.
48:41I just say that I smell a shark repellent.
48:44Oh, I smell a shark repellent.
48:48I think it's a great, great piece of science.
48:50It could be impregnated into wetsuits or sunscreens.
48:53And it's like widening the gap, I think, between sharks and people.
48:57I think this is how science can come together
49:00to have practical applications for conservation.
49:03And ultimately, we have healthier, more sustainable oceans.
49:08I think it's a great, great piece of science.
49:11It could be impregnated into wetsuits or sunscreens.
49:14And ultimately, we have healthier, more sustainable oceans.
49:24The end of the shark dive is also the end of the Atlantic expedition.
49:32A journey in which this ocean revealed how all our oceans once looked.
49:38I've spanned 3.5 billion years of the ocean's evolution in one trip.
49:43And that's quite something.
49:48This ocean has played a critical role in our history.
49:53But it's difficult to assess the impact we could be having on its future.
49:58The Atlantic is just being abused.
50:00And I don't think anyone knows what the consequences are.
50:03But we know that the consequences, whatever they are, are very serious.
50:07We can't continue to take it for granted.
50:14The Atlantic Ocean
50:18The Atlantic Ocean
50:21The Atlantic Ocean
50:24The Atlantic Ocean
50:27The Atlantic Ocean
50:30The Atlantic Ocean
50:33The Atlantic Ocean
50:36The Atlantic Ocean
50:39The Atlantic Ocean
50:42The Atlantic Ocean
50:45The Atlantic Ocean