Man, voice-over: I'm Steve Backshall, a naturalist and explorer.

Man: 3, 2, 1, go.

[Splash] Backshall, voice-over: I've been exploring the world's oceans for the last 30 years.

[Through respirator] Oh, wow!

They're one of the last frontiers of the unknown.

I feel like someone's underwear on the washing line in a high wind!

I've come to Mexico's Eastern Pacific... Now, looking at it, it's clear why there's so much potential here.

Go!

to help protect one of the most persecuted creatures on the planet.

We dropped down, and already circling us!

At least a dozen sharks!

Right now, sharks are under threat like never before.

This fishing boat is illegal.

On this "Expedition," I'm diving unexplored waters...

The thought that no one has ever seen this before... is absolutely mind-blowing!

to find new shark hotspots... A whale shark just cruising past us!

and protect them.

Unbelievable!

♪ [Sea gulls crying] ♪ This is our boat, the "Quino."

For the next 12 days, it's gonna be home, pretty much like our "Expedition" base camp.

From here, we head out into the Sea of Cortez and then to the big blue of the Eastern Pacific.

♪ Backshall, voice-over: I've come to Mexico to explore the Revillagigedo Archipelago.

It lies at the meeting point of two massive ocean currents, and the area is renowned for its rich marine life.

We have one remote island in our sights: Clarion.

Mauricio!

Very well.

Good to see you!

Good to see you.

Backshall: So this expedition has many different goals, and to achieve them all, we've got lots of different people.

So we have filmmakers, divers, marine biologists, conservationists, scientists, shark biologists.

And all of that takes an enormous amount of equipment.

Man, over walkie-talkie: I don't know.

[Indistinct].

Backshall, voice-over: Running the ship is Captain Julio.

He'll take us over 700 kilometers into the open ocean to reach the extreme edge of the archipelago.

Captain: I don't like the ports.

Ha ha ha!

I like the ocean.

♪ Backshall, voice-over: Dive supervisor Scott Carnahan and I have worked together for years.

It's his job to keep us all safe underwater.

Carnahan: There's a lot of stuff that can happen during these scuba-diving offshore expeditions.

You've all kinds of issues with decompression sickness, you have gas embolisms, you have people getting lost at sea.

So there's a lot of details that need to be worried about as you're doing this open-ocean travel.

♪ Backshall, voice-over: While Scott looks after our safety underwater, remote trauma specialist Dr. Charlotte Haldane is our onboard medic.

Haldane: Obviously, these guys are going diving [indistinct] at other places, and these guys are super-experienced.

But even the most experienced people occasionally can get problems with their lungs, so...

Your lives are literally in my hands!

Ha ha!

Scary, isn't it?

Backshall, voice-over: Joining us is shark biologist Mauricio Hoyos.

He's dived with sharks all over the world, but this archipelago is his backyard.

Hoyos: We have a lot of species of sharks in Revillagigedo Archipelago.

We have up to 9 species of sharks, like the Galapagos shark, the silvertip, the scalloped hammerhead.

So it's very important for us to gather as much information as possible about all these species, because we really want to protect them.

♪ Backshall, voice-over: The Revillagigedo National Park is the largest marine-protected area in North America.

3 islands in the archipelago have been well-dived... but one island is so remote, it's virtually unknown.

Mauricio believes it could be special.

We hope to discover whether Clarion Island could be the holy grail for shark conservation: a shark nursery.

Sharks come to this archipelago because it's peppered with sea mounts-- submerged volcanoes which sharks use as stopping-off points to rest, feed, and shelter on their long ocean migrations.

Where you have these small sea mounts, they become such an attractant for life and they can be some of the most abundant, some of the most intense places for marine life anywhere on the planet, and because of that, they are vitally important.

Their protection is the secret to the survival of our oceans.

Backshall, voice-over: For Mauricio, satellite tagging is the key to protecting sharks.

He fixes transmitters onto them to track their routes through the ocean.

The moment a shark leaves a marine-protected area, it's vulnerable to commercial fishing.

If Mauricio can tag a migratory shark here, then he can identify its marine migration corridor and push for more protection.

So this is our little lab?

Oh, yes, a lot of toys.

I would like to bring 2 ball spheres.

Yeah.

So in one, I will have the solid transmitter.

I would like to tag a whale shark, Galapagos, or scalloped hammerhead with the mini-ball.

Backshall, voice-over: To do that, he needs to get close enough to jab it with his spear, inserting the satellite transmitter, almost painlessly.

When we set these transmitters, it's like a mosquito bite.

This transmitter can get information about the temperature and depth preferences and also the location.

So this one is programmed for 6 months.

It's gonna be storaging all the information about this-- the behavior of this specific animal.

Have you ever had a bad reaction from a shark from-- From, uh, big Galapagos.

Really?

Big Galapagos.

Yes.

It got upset?

She was mad at me.

She was like 3 meters.

And she came to me, she was looking at me, and I just put myself between the rock and the shark, and then she was better, but that's the only one.

Most of the cases, they just go away.

Obviously, we just gotta hope that we have the conditions on our side, that we get the chance to do as much as possible.

Yeah.

It's really important to use all this technology in order to understand the migratory patterns of these animals, because when they are inside of Revillagigedo National Park, they are protected, but when they go, they do not respect human boundaries.

Backshall, voice-over: Scientists don't yet know exactly which routes sharks take from one hotspot to another.

If they can gather enough satellite data from multiple sharks, they'll be able to lock this down.

Once known, sharks can be protected wherever they go.

♪ Marine biologist Dr. Frida Lara has studied shark behavior in this archipelago for years.

She's excited about our expedition endpoint: Clarion.

Lara: Clarion is the most-unexplored island in the archipelago.

So I think it's very important to go there and register the species that are around.

Backshall, voice-over: Diving this far out in the Pacific, our biggest concern is safety.

Backshall: We're gonna be diving way out in the eastern Pacific on sites that have potentially never been dived before.

What are the potential risks here?

Well, the biggest risks are the ones we don't know about.

You know, the depths aren't known, the currents aren't known, the sea states, the visibilities.

We are a full day away from the other islands and then another day back to the mainland, so we're as far offshore in Mexico as we can get.

I don't think I've ever headed out on an expedition with quite so much to try and achieve in so short a space of time with the potential of weather and conditions and sea state and everything that-- it's--this is a big one.

Absolutely.

Absolutely.

A lot of things that could go wrong.

♪ Backshall, voice-over: Our first stop is San Benedicto, a safe dive site 370 kilometers from the mainland, where we'll test our dive gear.

♪ From there, we'll head to Roca Partida, a sea mount, where Mauricio plans to tag a migratory shark.

♪ It'll be another 20 hours to reach Clarion, where our true underwater exploration begins.

♪ With our first dive site still a day away, Captain Julio is planning to power on through the night.

♪ Haldane: Welcome to downstairs.

People's [indistinct] and their [indistinct].

Backshall, voice-over: For us, it's a chance to get our heads down.

This is the cabin where we're sleeping in here, which is pretty cozy.

I think it's one in, one out, really, to get changed.

Ha ha!

'Cause everyone's got their own timing, but hopefully a little space, so, yeah.

It's cozy.

Backshall: You get used to boat life pretty quick.

It's all a bit cramped, but it's kind of--kind of nice and cozy.

It's all right as long as no one's too smelly or too snorey.

I'm pretty sure it's not me.

[Sniffing] ♪ Backshall: Heyy!!

We picked up a small pod of bottlenose dolphins!

♪ So as the boat drives its way through the blue, it creates a pressure wave at the front, and they're just surfing it.

It's one of the happiest sights in nature.

Any day you see this is automatically a good day, and I'm taking this as a good sign for our expedition.

♪ Backshall, voice-over: After 30 hours at the helm, Captain Julio has San Benedicto in his sights.

Captain: We closer.

We almost there.

Backshall: OK, all right.

How long do you estimate before we can be at anchor?

Captain: 50 minutes we drop the anchor in.

Great.

Thank you.

All right.

OK, Steve.

♪ Backshall, voice-over: As soon as we drop anchor, we can get started.

So this is our first island-- San Benedicto.

And it's big!

It's bigger than I was expecting.

So this is the summit of a volcano, which last erupted in about 1953.

So dramatic, isn't it?

It's like the perfect volcanic crater.

But even more dramatic is what's going on below the waves.

Those slopes just drop straight down through kilometers of water to the abyssal plain below us now, and that's 3,700 meters.

So nearly 4 kilometers-- more than 2 miles in depth.

♪ Backshall, voice-over: This is a known dive site, so the perfect place to test all our equipment.

Below the surface, these volcanic cliffs are cloaked by shoals of fish... [Chain rattling] and attract large numbers of sharks.

Carnahan: We'll slowly get loaded.

We have the other dive team.

For dive times, we're looking at a open-circuit team dive time.

20, maximum 30 minutes.

Does anybody have any questions?

Backshall, voice-over: With many expeditions under our belt, Scott and I have a 100% safety record, and we want to keep it that way.

Carnahan: Let's make sure we get our BCDs and all the stuff we need doublechecked-- your fins, your weight belts.

Let's go ahead and cautiously, carefully get yourself ready and make sure you don't forget anything, and let's go.

There's a lot of stuff that can potentially go wrong.

A lot of the equipment they're using for the first time on this trip, and we're adjusting a lot of it.

There are also a lot of just environmental conditions.

You know, there is a lot of waves, a lot of current.

Backshall: Forget any one little thing, and you have to call the dive.

so it's just taking over, making sure you got everything, and, uh...preparing.

♪ Backshall, voice-over: To maximize my dive time, I'm carrying 2 cylinders of compressed air weighing about 50 kilos.

[Belt rattling] And if you find when you get in right away, if you think you're gonna do a little trial, maybe it's gonna be-- if you feel like you're just ultra-heavy, you can pass me that up.

Yeah.

Heavy's--heavy's fine.

I can balance on heavy.

It's the too light I can't deal with.

Backshall, voice-over: With extra weight on my belt, moving around the boat is pretty much impossible.

Bailout is off.

Backshall, voice-over: If the system fails, I also have a back-up bailout.

OK. [Air hissing] Primary.

Tank.

Mm-hmm.

Primary tank.

Backshall, voice-over: We check and doublecheck everything on the surface.

A failure at depth is unthinkable.

I'm happy.

Are you guys completely ready to go diving over there?

Everybody's completely ready, 100%?

Backshall, voice-over: We'll dive in buddy pairs, watching each other's backs in case a shark approaches from behind.

Carnahan: 3, 2, 1, go!

[Splash] ♪ Divers in the water 9:33.

Backshall, voice-over: We also need to test our new underwater communications equipment, which allows us to talk underwater.

Radio check.

Radio check.

Backshall, voice-over: The comms should allow us to speak to Scott down to 30 meters.

[Backshall speaking indistinctly over respirator] I can hear you great, Scott.

Copy that, Steve.

I have you 100% clear.

Backshall, voice-over: It works like an underwater walkie-talkie, using the density of the water to transmit signals back and forth between us.

It's a crucial line of communication, especially out here in the open ocean.

Hoyos: Scott, I am having some issue with my ears.

Copy Mauricio is that you're having problems with your ears?

Hoyos: Yes, yes.

I am trying to go down slowly.

OK. Press that mask up into your nose and take it slow.

Diving's always a complex thing to deal with.

With all the preparation in the world, right now Mauricio's having an ear issue upon descent.

That increased pressure was putting pressure on the outside of his ears, and he's having a hard time equalizing.

♪ Backshall: This is Steve.

Can I get a status update on Mauricio, please?

Hoyos: I cannot go lower than this.

I don't know what's wrong with my left ear.

♪ Backshall, voice-over: Mauricio has no choice but to wait at a safety stop 10 meters from the surface.

If his ears don't clear, he'll have to return to the boat.

The rest of us dropped to 30 meters to put our gear to the test, and I want to see what shark species are here.

♪ Oh, wow!

♪ We've dropped down... to the bottom... and they're already circling us!

At least a dozen sharks.

We've got Sukis, at least one big Galapagos shark, but probably the most inquisitive are these... silvertip sharks.

They have a very dramatic trailing edge that's bright, bright white to the pectoral fins and the dorsal fin.

I think they're one of my favorite sharks in the world.

♪ Really, really beautiful little sharks.

♪ Backshall, voice-over: And a giant manta, a close relative of the shark's.

♪ Mauricio is coming to the surface.

He had problems with his ears.

He is coming up right now.

So, what happened, Mauricio?

I couldn't, uh, equalize.

And I tried to go deeper, but couldn't.

And I felt like, "No, no, no."

You OK for now?

Hoyos: Yeah, yeah.

You're good for now?

Thank you.

♪ Um, guys, this has never happened to me before... but the...the nose clips on the mask have fallen off.

I cannot equalize.

I may at some stage have to rip the mask off.

Yeah, let's go ahead and abort this dive.

Let's go ahead and abort this dive.

Backshall: Copy that.

Yeah, all divers to the surface.

All divers, start the ascent.

Carnahan: Here he comes right here.

That wasn't good.

What actually happened or what did you-- I just--I was trying to equalize, and it--and it wouldn't work.

So I had no choice but to rip it off and come to the surface in Frida's extra mask.

Um...but when you're whatever I was-- at least 30 meters below the surface, it's, uh-- it's pretty scary.

Carnahan: Absolutely.

Now that we have everyone back on the surface, let's go ahead and we'll get back to the main boat.

And then figure out a way that we can get down without problems?

♪ Backshall, voice-over: Exploration diving is highly technical.

and exactly why test dives are essential.

We now need to refine our gear and plan our next move.

My feeling is just that when we work in a big group, when there's maybe 8 of us in the water, that we're quite unwieldy.

So I'm wondering-- just throwing this out there-- how about we split teams and you two work together, and I work with Frida and, you know, divide and conquer?

I just think it doubles our chances.

Hoyos: Exactly.

Naturally, it's way better to be in small group if you are about to dive a shark.

I mean, if you have a lot of people, they go away.

So I think that it's way better.

OK.

I think we have our plan.

Carnahan: That sounds great.

Sounds really good.

♪ Backshall: So, we've had a strong start, but it's brought into sharp focus quite how much we have to achieve in a short space of time.

From here, we're heading ever west.

These islands are kind of pointing right out into the middle of the Pacific.

And while here it's kind of windswept and exposed and feels like the middle of nowhere, comparatively, this is-- this is known territory.

Out there is where the real exploration's gonna happen.

♪ Backshall, voice-over: From here, we head 12 hours and 120 kilometers west to Roca Partida.

It's a known stop-off for migratory sharks-- the perfect place for Mauricio to tag one.

♪ But that's still a day's travel away.

Aaah!

Ha ha!

All of a sudden, everyone's up and doing stuff.

They're writing, they're sorting out their kit.

I'm taking the opportunity to exercise.

And all of a sudden, it's just really nice time to kind of figure out what you're gonna do on the expedition and try and get everything sorted.

♪ We are riding to Roca Partida.

♪ [Chain rattling] Backshall, voice-over: Roca Partida is a sea mount, a volcanic pinnacle in the middle of the ocean.

This is just the tip.

Beneath the surface, this sea mount drops 3,400 meters down to the ocean floor.

♪ It formed when an underwater volcano erupted, spilling lava that hardened as it met the water.

Over time and many more eruptions, it grew until it reached the surface.

♪ So, this is it-- Roca Partida.

This is the-- the thing that has brought us in across all that ocean.

And it's the most dramatic representation you could ever have of how important a sea mount is.

I mean, just that tiny, teeny little rock attracts so much life.

Backshall, voice-over: This volcanic pinnacle is the oceanic equivalent of an oasis, a stopping-off place for open-ocean migrants, a focal point for life, and perhaps, most importantly, an abundant marine canteen full of food.

But the fierce currents that smash this rock can be incredibly hazardous for divers.

We're watching out for the current, is our main factor today.

We really need to make sure no one's getting blown off the rocks.

We're gonna split up into 2 teams, 2 small teams, 2 4-person teams.

We'll go out.

We'll be the shark team, looking for good animal life; whereas the actual-- the science team which will be tagging your sharks.

Hoyos: So, my mission is to tag a highly migratory shark.

So we could tag a whale shark, a silvertip, a big Galapagos.

I have a solid transmitter in my spear gun, and an acoustic transmitter in my pole spear.

Backshall, voice-over: The boat is packed with tons of technical dive gear, camera kit, and scientific equipment.

But out in the open ocean, one of the most important pieces of kit is a locator beacon.

[Beeping] When you set it off, a ship will know where to find you, particularly this ship.

So if I get carried by the current out into the Pacific, this is the only thing that's gonna allow this boat to come and find me.

So we all have to wear these at all times.

Backshall, voice-over: Charlotte is a remote trauma medic and dive master.

Haldane: Animals are unpredictable, and whilst we obviously know that sharks aren't out there to get to us, sometimes rapid movements with lots of people in the water can change their behavior and don't really know anything about this area.

They're not used to seeing divers, so you can't always predict how they're gonna react.

So from my side, it's always plan for the worst and hope for the best.

And so, you know, I've got everything ready just in case, but... ♪ Backshall, voice-over: With my dive buddy Frida, I will explore the north side of the rock.

Everybody has fins and masks?

Backshall, voice-over: Mauricio and the tagging team will take the south side.

Haldane: Just before you get in, just a reminder, we're in quite a dangerous location today with the current.

Keep an eye on your bottom times, and, yeah, just be tied to the buddy system today, just 'cause of the current, yeah?

Everyone happy?

Yep.

Man: Think so.

♪ One of the things that keeps you safe when you're diving is that you have a dive buddy and you tend to stay really close together.

But currents can very easily split you apart, just from one tiny lapse in concentration.

So, yeah, the current is probably the biggest worry today, and if they get that wrong, there is just ocean.

Backshall, voice-over: To tag a shark, Mauricio needs to get in close-- not easy in these strong currents.

Backshall: So, all of the currents and the movements of the tide are gonna wash up against the sea mount and create pressure-- that could be downdrafts, updrafts sweeping around the side of it.

and potentially underwater, it could be pretty hairy here.

And below the waves, who knows.

It could be, you know, one of the greatest dives on the planet.

It could be utterly terrifying.

And we won't know until we get wet.

OK, should we get this on?

Yeah.

Carnahan: Is everybody ready?

All: Yeah.

3, 2, 1, go.

♪ Backshall, voice-over: Roca Partida is my idea of a perfect dive site.

I'm desperate to see what's down here.

Backshall: The current is whipping... around the side of the sea mount... with such force, I can barely hold on.

♪ Whaaa!

I feel like someone's underwear on the washing line in a high wind!

Ha!

It's unbelievable!

Every once in a while, the current will try and take you straight down... and when the bottom is 100 meters below you, that's pretty frightening.

But look up there!

Look at all that life!

It's utterly, utterly staggering!

♪ Backshall, voice-over: Marine life is so abundant here because of the food, plankton, funneled up from the ocean's depths.

The fish eat the plankton, and the sharks eat the fish.

It is the most perfect example of why sea mounts are so important.

You got this one tiny abrupt pinnacle coming up out of the deep, and everything gets attracted into it.

Vast shoals of fish, and the predators coming in to feast on them.

I mean, look at that shoal of jacks up there.

It's huge!

And the sharks circling around us!

Look at the size of that tuna!

Oh, my gosh!

It's the size of a cow!

That is amazing!

♪ It's been 20 years since I've seen a tuna that size.

It's something incredibly special.

♪ Oh, my gosh!

Look!

A whale shark!

♪ The biggest fish in our oceans!

Just cruising past us!

♪ Absolutely astounding!

It's coming straight for me!

Unbelievable!

♪ It's got an entourage of remoras and black jacks, those dark fish hanging underneath it.

The remoras are sucker fish and getting a free ride, hanging onto the underside of the whale shark.

And the black jacks are riding the pressure wave that it creates, just like the dolphin would do.

♪ Backshall, voice-over: Whale sharks are migratory, and we don't know where they mate.

where they give birth, or what route they take through the ocean.

This one is a female, exactly what Mauricio needs.

He wants to fix the satellite tag behind her dorsal fin.

Mauricio has to approach from above and get within 2 meters before he pulls the trigger.

♪ Hoyos: OK, success.

It was a female.

How big do you think it was?

Man: About 6 or 7 meters.

Yeah?

Yeah, I was focusing the dorsal fin.

So I was like, "Whoa!"

It was not small.

It was good size.

Yeah.

So 6 months later this day-- 6 months, we will know everything about the temperature and depth preferences and also the location for the migration when they go from here.

Haldane: You guys are keen to come back.

We are Team "A"!

Ha ha!

[Laughter] The dream team.

♪ Backshall, voice-over: Like all sharks, whale sharks are highly valued for their meat, fins, and oil.

When this shark leaves the marine-protected area, it's at risk from commercial fishing, which is why Mauricio wants to tag one.

And he's made it back to the boat sooner that I'd expected.

Heyyy!

Amazing!

Right at the beginning.

Backshall: Good work!

Good work!

Team, that is amazing!

It's coming together.

Yeah!

Backshall, voice-over: With the whale shark tagged, Mauricio will now know its every move in the open ocean for the next 6 months.

He'll feed this information into a groundbreaking scientific database, a lifeline for the future of sharks.

[Clanging] Lunch is ready!

Backshall, voice-over: The true engine room on any dive boat is the galley.

Sopa de Lentejas-- Lentil soup.

Backshall, voice-over: Chef Miguel and assistant Edgar are key members of the team.

Great chef!

And the main course is [indistinct] fajitas with flour tortillas, [indistinct], guacamole, and beans.

Backshall, voice-over: After every dive, we rest for about 2 hours to allow our bodies to recover, which gives me time to reflect on why we're here.

Each year, we may take a quarter of a billion sharks from the world's oceans, 73 million of which are taken purely for their fins, which ends up in shark fin soup.

And unless we do something to stem the tide, then these animals will disappear.

So it's a pretty bleak outlook.

And then you come somewhere like here, and you see sharks well-protected and doing well, and it gives you hope.

But there has to be strong, stringent protection for places like this archipelago, the Galapagos, Cocos, Mount Palau, and the other shark sanctuaries around the world.

Backshall, voice-over: With the tagging complete, we're heading 20 hours west.

Clarion Island lies at the meeting point of 2 ocean forces: the California and the North Equatorial currents.

♪ I hope it could be a marine paradise, but sitting on the extreme edge of the archipelago, it also makes it highly vulnerable to illegal fishing boats coming in and mucking up the sea floor.

♪ Clarion's remote location means that 90% of its waters are unexplored.

♪ Just a few kilometers away from Clarion, it's clear we're not alone.

♪ Well, this is as perfect an example of why this expedition is so important.

So this fishing boat is right in the marine-protected area.

This is a UNESCO World Heritage Site.

It is an absolute no-take zone.

Their presence here is illegal.

You can see the temptation.

I'm not a fisherman myself, but if you were and you knew that there are hundreds of miles of completely empty open ocean, and then this place, where life is flourishing, and you thought you could sneak in, then you probably would.

And that, plain and simple, is why they're here.

You know, they're not here by accident.

Every one of these boats has GPS, has all the charts, has all the maps, and knows where the limits of the parks are, and they also know that inside those limits is where the best fishing's gonna be.

And here, this is a relatively small fishing vessel, but a big factory fishing boat kind of coming powering through here could decimate the area in one single fishing trip.

And that's why the information we can bring back is so critical.

♪ [Phone dialing] Backshall, voice-over: For Mauricio, seeing this particular fishing boat is a blow.

He's seen it here before, so it's a repeat offender.

Yeah, I have bad news.

Yep.

Fishing.

I--I took some footage.

OK, I will give you the footage as soon as we get to [indistinct].

Backshall, voice-over: Sharks are slow breeders.

Many species only have a few young at a time and take a long time to reach maturity.

When commercial fishing boats catch one shark, it's not just one life lost.

It can be a whole generation.

Mauricio believes that Clarion could be a shark nursery, the holy grail for conservationists.

He wants to protect it, but to do that, he needs hard evidence that shark pups are here.

Uh, we arrive Clarion Island.

We're very close, so... 1 mile.

♪ If you find a place where, fish, particularly animals like sharks, have their breeding grounds and their nurseries and you protect those places, it has a disproportionate effect.

Protecting somewhere like this is the future for sharks.

Backshall, voice-over: As we come into anchor, there's a welcoming party.

♪ A humpback mother and calf just cruised on past.

♪ But almost more spectacular is the sounds they're making.

The song of the humpback is one of the most complex and beautiful in the entire animal kingdom.

And when they're going off like this, it's just--it makes you want to cry.

[Whale song] The most incredible thing about humpback communication is that it's different depending on where you are.

Different populations of humpbacks have very distinct songs, so much so that scientists have described them as being like dialects and, in some cases, even as being like different languages.

So, the humpbacks here in this part of the world migrating up and down the western seaboard of North America have a different song to those that are found in the Arabian Gulf, and it's just like tribes of different animals that have their own languages.

People have been trying for generations to put into words the song of the humpback, and I--I think it's a waste of time.

You just have to listen.

[Whale song] Backshall, voice-over: It may not just be whales bringing their young here.

Mauricio's acoustic tagging has shown that pregnant sharks might be coming here to give birth.

If we can prove that Clarion is a shark nursery, Mauricio will have the evidence he needs to persuade the Mexican Navy to send a patrol vessel here to enforce the rules and punish anyone that breaks them.

What now?

Is there anything we can do here that can help with this mission?

I think we can prepare some baited cameras-- a canister with some attractant that can be fish, and then is attached with a stick to a Go-Pro and is floating on the bottom of the ocean for one hour and is recording all the marine life that is attracted by this bait.

Backshall, voice-over: These Baited Remote Underwater Video Cameras, or BRUVS, have never been used here before.

While Mauricio and Frida attempt to capture images of baby sharks, I want to find out what else is here.

Now looking at it, it's clear why there's so much potential here.

It has all the properties that you would need for a sublime, perfect place for life to aggregate.

It has the meeting of the two currents.

It has its exposure, the fact that there's nothing else for 100 miles in every direction.

It should be an absolute haven for marine life.

Backshall, voice-over: I'm heading to the north of the island, which is smashed by the California and North Equatorial Currents.

Where we're going, there's been no recorded dives, and it's ripe for exploration.

It is about as dramatic a place as you could possibly wish for to start exploring.

Off in the distance are these incredible pinnacles.

They look like something out of Monument Valley.

They look like something out of a western movie, except surrounded by the Pacific Ocean.

And we have lots and lots of methods at our disposal to try and find where we should start.

And we just have to drop in and start looking, start running transects-- so an organized search pattern.

♪ Backshall, voice-over: To help us cover maximum ground, I've got a secret weapon.

It's called a DPV, or a Diver Propulsion Vehicle.

It has a propeller at the back, which can drive us along underwater far faster than we'd be able to swim.

♪ Dolphins!

Backshall: Oh, whoa, whoa!

[Indistinct] Backshall: So, already, we've got huge amounts of dolphins here, whales, all of which is a sign of productivity in the water.

So, plankton is small fish for the whales, slightly larger fish for the dolphins and equally for sharks, too.

So, although, from a diving perspective, this is very, very little known, very clearly, from a wildlife perspective, it's really special.

Carnahan: How do you feel about him starting here and wrapping?

Or do you want to go further and start on the next cliff face?

Backshall: Well, let's at least get around this corner and see what happens, shall we, if everyone's happy with that?

♪ Backshall, voice-over: While we dive the choppy waters on the northwest of Clarion, the science team set up their baited cameras in a shallow, sheltered area which Mauricio hopes could be a shark nursery.

Hoyos: This is the first time that we are using BRUVS in the nursery area.

So I think that it's gonna be interesting, because we can actually see the actual babies in the area.

So it's very important to identify these places in order to protect a very important lifecycle stage of this species.

♪ Backshall, voice-over: If they can capture baby sharks on camera, Mauricio will have the proof he needs to push for increased protection of Clarion.

♪ Hoyos: I saw, like, 3 baby Galapagos, but at the end, we saw a really, really tiny one, like this big-- maybe 2 years old-- getting close to the BRUV.

So I am sure that we will be able to get on film these little babies, so this is the perfect nursery area for the Galapagos, because it's a shallow area with a lot of food, and we didn't see any predators.

So that's what you are looking for as a shark mom.

Ha!

If you want to deliver your pups, do it in these kind of places, away from the big predators with a lot of food.

Backshall, voice-over: While Mauricio and Frida head back to the boat, we dive down to begin our exploration.

Backshall: 3, 2, 1, go.

[Splash] [Beeping] Right now, I'm just marking this spot, just so we know we can record exactly where we're starting, where we're finishing, what sections of the coastline we're exploring.

♪ Backshall: This is so cool.

Well, this is a bit of a game-changer in terms of how much ground you can cover.

♪ Absolutely enormous school of jacks around us!

These are themselves predatory fish, but they're also very important food for sharks and other predators like dolphins.

The waters keep changing from tropical warm to temperate cold, and that just explains why there's so much life.

♪ Backshall, voice-over: Smaller fish like these are the perfect mouthful for baby sharks.

♪ Backshall: Turtle!

Turtle!

This is unbelievable!

Look at all the sharks!

Hello, fella!

♪ Well, in terms of underwater vigils, it doesn't get any more spectacular than this.

And the thought that no one has ever seen this before is absolutely mind-blowing!

♪ Oh, a whale dolphin!

Amazing!

♪ Oh, that's a huge pod of dolphins!

Wow!

That's totally epic!

Wowowow!

Wow!

Wow!

Wow!

Whayyy!

It's showing off now!

A massive tortoise.

A [indistinct] things like this is the most incredible sight you could ever have of a healthy marine ecosystem.

What an experience.

Anywhere else in the world, and this would be a renowned dive site that people would travel thousands of miles to come to.

And here, we're the first human beings ever to dive it.

That that's possible in this century is almost unbelievable.

Backshall, voice-over: These waters are richer than I could ever have imagined.

Backshall: Oh ho!

Wow!

Oh, my goodness!

Baby shark!

How cool is that?

Backshall, voice-over: It's quickly spooked by my presence, but it's a real sign that this could be a shark nursery.

♪ Don't look at my air gauges.

Ha ha!

I think on this one occasion, I may be allowed to come up with next to nothing.

That was unbelievable.

Absolutely unbelievable.

Saw young pups, so I'm not 100% sure what species they were, but this sort of size, and I would probably say Galapagos sharks.

Carnahan: That's awesome.

And then a real mix of marine life.

Some of it looks like it should be in temperate sea, some of it looks like it should be in tropical, all living in the same place.

Carnahan: Yeah, amazing.

Yeah, it really is.

It's like 2 different aquariums.

They've just all been mixed together.

It's--it's not like anywhere I've seen before.

It's up there with some of the best dive sites I've ever done, and I've been diving for 30 years.

And we were the first people ever to see it.

People would cross oceans to see that, wouldn't they?

Hoyos: Definitely.

We were just the first, dude.

[Engine roaring] Backshall, voice-over: To explore an undiscovered marine paradise is a dream come true, but our goal is to prove this is a shark nursery.

To properly protect these waters, we need hard evidence.

Our hopes now rest on Mauricio and Frida's underwater camera.

Oh, look!

Jack.

Oy yo yo!

Dolphins!

Wow!

Yo, a ray!

Backshall: It's a stingray.

Hoyos: Yeah.

Lara: Yeah.

Oh, octopus!

Whoa!

We saw a few.

That's amazing!

Lara: Ha ha!

That is so, so cool.

What a great shot!

Ha ha ha!

Also, quite a lot of the sharks round here feed on octopus, don't they?

They could.

He put himself into a dangerous position.

Oh!

Baby, baby.

Baby Galapagos.

So, how can you tell that this one is a youngster?

It's super slender, and they are super tiny.

It was like this big.

What would this lead you to believe is going on here?

Well, I think that the pregnant females are coming to this area.

It's shallow.

It has a lot of food.

It's protected.

And maybe the babies stay here for a few years until they are big enough to do their migration to other areas.

So you think it's possible that where we are right now could be somewhere where just the youngsters hang out, I mean, effectively a nursery for Galapagos sharks.

Absolutely.

So, protecting here is not just important for here.

Exactly.

It's important for all sharks in this part of the world.

Exactly.

Sharks do not respect human boundaries.

They move all over the planet, and it's important to protect them not just in isolated nations but internationally.

So, do you think you've gathered enough evidence to go to the parks and try and get increased protection for where we are right now?

Yeah, yeah, yeah.

Definitely.

Lara: Yeah.

I think they need the support from the Navy, too, to be able to--to manage this area of the park, stopping these fishing boats that are going around, and even, like, take their fishing gear as a consequence of their activities here.

♪ Backshall: I first started working in shark conservation when I was in my late teens.

And I was saying things like, "Sharks are worth more alive than dead" and "They're not the man-eating monsters they're made out to be."

and "We have to protect the seas, otherwise we will lose them."

And I'm nearly 50, and I'm still saying exactly the same things.

♪ Backshall, voice-over: With illegal fishing boats able to enter this marine-protected area so easily, sharks here don't stand a chance.

When they're caught in large numbers, they can't reproduce fast enough to keep the population going.

Backshall: The UN has deduced that by the year 2050, all fish in our oceans will be commercially extinct.

But the way around that is to protect big areas of our oceans, but you don't just protect any old place.

It has to be the right spot.

Somewhere like here.

Backshall, voice-over: Finding and protecting shark nurseries and their migration corridors is crucial.

Mauricio's satellite tagging data will feed into a global database, providing scientists with the ammunition they need to defend our ocean's most persecuted creatures.

It's gonna take real determination.

It's gonna need people like Mauricio and Frida, who are prepared to give everything to try and save them.

And it's gonna take marine-protected areas like this.

♪ Announcer: "Expedition with Steve Backshall" is available on Amazon Prime Video.

♪