Steve Backshall: This is the third-largest rainforest in the world, arguably the most biodiverse place on the continent.

I'm Steve Backshall, a naturalist and explorer.

Look at the size of these footprints!

That's my hand inside it.

♪ We've come to Gabon...

Welcome to paradise.

Give you one of these!

Cool, man.

Steve, voice-over: to explore an unmapped area of rainforest.

Utterly amazing.

To be heading there, into the unknown, where no one's been before, we have no information whatsoever, it is about as exciting as expeditions get.

Our goal is to discover a new population of chimpanzees.

Woman: I have a nest!

Steve: That's amazing!

Steve, voice-over: Standing between us and the unknown is a thundering river canyon.

It's kept people away from this rainforest for generations.

Man: This is a place where the Nyanga River disappear.

I can't believe it.

Man: People will say to me, "Don't go there; I'm not sure you'll come back."

Steve: Beyond the canyon lies a jungle paradise that has never been explored.

Every single step, every single paddle stroke will be true exploration.

[Woman whimpers] ♪ Steve: Gabon is one of the most densely forested countries on the planet, home to iconic primates like chimpanzees, gorillas, and monkeys.

♪ On the West Coast of Africa, Gabon is one of the most important wilderness areas left on Earth.

On this expedition, we're heading to the Moukalaba-Doudou National Park, into unknown, unexplored, and unmapped terrain.

The only way in is by river.

♪ That is most definitely a bridge.

♪ Quite glad to be over that.

Heh!

Steve, voice-over: Our goal is to find unknown populations of chimpanzees and other endangered animals to understand how we can protect this vital ecosystem.

I'm teaming up with chimpanzee specialist Alessandra Mascaro.

She's spent years studying primates in the north of the country.

I am really, really excited.

I have never been here, but I'm sure we will observe so many species in this area.

Steve: It's a national park.

It has some degree of protection, but what it needs is World Heritage-site status.

We will have the possibility to collect new datas and samples about primates or other species in the unknown zone.

♪ Steve: If we could discover chimpanzees in this unknown zone, it will take the area a step closer to winning UNESCO World Heritage status and increased protection.

♪ Steve: Joining us on this expedition is local jungle guide Ghislain Bouassa.

♪ Ghislain: This will be the first time I've been on the river like this, uh, so, yeah, it's exciting.

Longer than I've paddled before.

It's a good--good thing, is that we're going downstream.

Ha ha ha!

Steve, voice-over: To take on this river, we're using inflatable canoes.

For an expedition like this, getting us places that you just simply wouldn't be able to get to otherwise, they're perfect.

Expedition kayaker and medic Tom McLay is in charge of safety.

Tom: If you fall out in a rapid, the way that you position yourself is feet going first down the river and lying on your back.

So this first section, the first 14 kilometers, is well-known and mapped, then we hit a canyon, a gorge, and beyond that, who knows?

♪ This canyon is a gateway to the unknown zone, an unmapped area of jungle cut off by mountains.

♪ Using the river as our highway, we'll cross this zone from east to west, exploring untouched rainforest in search of primates.

♪ Before we can get on the river, local customs mean we need a blessing for our expedition.

Alessandra: Oh.

Ghislain: So he's saying that it's the food of the spirits, of the ancestor, so if we want to-- to discuss with them, we have to feed them first so they--they will be happy.

[Man shouts in native language, men repeat] [Speaks native language] Ghislain: He's wishing you a good trip along the river and in the forest.

[Steve exhales sharply] It's steaming, steaming hot.

We're already dripping with sweat.

[Men chatter in native language] ♪ Steve: Ahead of us lies a 14-kilometer paddle to reach the top of the canyon and our first camp.

♪ Tom: Crazy, huh?

[Whistles] And too hot for me.

Ha ha ha!

♪ Tom: You know what I call these canoes?

"The divorce boat" because if you put a couple in there, they always argue.

[Tom and Alessandra laugh] Steve: Look at the size of those trees over there!

Alessandra: Is a keys tree.

Certainly like skeletons, aren't they?

Yeah.

Steve, voice-over: Spiritual beliefs about the forest are strong.

Local legend warns the canyon is guarded by water spirits.

It's known as "Nyanga kotbalungi"-- "the place where the river disappears."

The river's huge.

It's really swollen, high.

There are swirls and boils and whirlpools.

It's really pretty intimidating.

Steve, voice-over: A boil is a dangerous pocket of air, generated when too much water is forced through rocks on the riverbed.

Tom: All of these try and destabilize any sort of boat that's on the river and will try and flip it over.

Oh!

Alessandra: It's OK. Steve: What is much more of a concern is that we're heading towards this big mountain ridge, and when the river gets there, it's going to force its way through a gorge or a canyon, and all of this mass of water is going to be constricted.

Steve, voice-over: The current is already incredibly powerful.

There's never been a recorded descent of the Nyanga River... [Distant animal screeching] and as our canoes speed up, I'm beginning to realize why.

Very fast--OK, keep paddling on your left-hand side, please.

And you're most stable when you've got your paddle in the water!

See that whirlpool to your right?

Look.

♪ Whirlpool, right here!

Whirlpool!

Look down!

Whirlpool!

[Suspenseful music playing] ♪ Tom: Stop, stop.

Stop, stop, stop, stop, stop.

Steve, voice-over: At 14 kilometers, the river drags us faster and faster towards the canyon.

It's time to get out and make camp.

[Steve grunts] Paddle, paddle, paddle.

On your left.

Where?

Well done, well done.

Left?

Tom: Right here.

Steve: Camp!

How's it look, Steve?

Yeah, it looks really good.

There's a good amount of space, few hammock spots, mostly tents, but I think we're all right.

Steve: All of this here would normally be riverbank, and these big trees would be completely exposed up on land, and instead, they're under probably a couple of meters of water, and you can see the force, that it's coming down around the trunks.

Steve, voice-over: It's rainy season, so this riverbank could flood in minutes without warning.

We need high ground.

[Ominous music playing] ♪ Steve: So when you're choosing a camp, the first thing you do is you look up.

If you have an old tree to the side of you, and there are branches above that could be, you know, eaten out by termites, dead and rotten, and that comes down, it can be easily a ton of wood.

But I've got a couple of young, but sturdy trees, so I'm just going to hang my hammock here.

Should be perfect.

Come to bottom, like this.

[Speaks indistinctly] Ha ha ha!

[Chuckling] Your bum's almost on the floor?

Alessandra: Ha ha!

[Insects chirping] Steve, voice-over: While the team sets up camp, Ghislain and I head out into the night, looking for signs of life, and don't have to look very far.

Steve: Ah.

He's lovely.

Yeah.

So, do you know what kind of tortoise this is, Ghislain?

So, this is, uh, the Kinixys erosa, the only land turtle that we have in Gabon.

Really?

Steve, voice-over: We found a hingeback tortoise.

They thrive in this moist forest, but, like so many animals here, they're under threat.

Tortoises are another animal that gets taken out of an environment really, really quickly if poaching is rife.

And, you know, sadly, one of the main reasons for that is that their defense mechanism is to pull themselves into their shell, which is pretty good for most of its natural predators, but it's the worst possible thing for avoiding a human being.

And to see this one here wandering around is a really, really good sign of how healthy this forest is and of how few human visitors it sees.

Steve, voice-over: This find is a great start, but I'm keen to discover many more endangered species like this.

Each and every animal we find will help build a case for stronger protection here.

[Distant animals chortling] Steve: We know so little about what happens to the river now.

Yeah.

Are you--are you worried, are you concerned about what is downstream?

You know what?

I'll be honest with you, Steve.

I didn't sleep the whole night.

I'm not kidding.

I didn't sleep.

[Suspenseful music playing] Steve, voice-over: I need to see this canyon with my own eyes and discover why it has such a terrifying reputation.

Steve: If you listen... you can hear the river.

Well, it doesn't sound like a river anymore.

It sounds like a waterfall.

I can see water!

[Distant bird squawks] I can't believe it.

That entire, massive river has narrowed down into... less than 10 meters.

♪ Whoa, there are some massive whirlpools being generated here.

Steve, voice-over: I can see why it's kept generations of local people out of this part of the jungle.

Ghislain: This is a place where the Nyanga River disappear.

People say to me, "Don't go there because if you go there, I'm not sure you'll come back."

Heh heh!

Steve, voice-over: Luckily, we can go inside the canyon without getting our feet wet.

Tom: It's just like a funnel.

The river's like this, and it's just [whooshing sound].

Steve: And you can see it abruptly getting very narrow.

It turns into an alleyway, doesn't it?

[Tense music playing] ♪ Steve, voice-over: The drone's behaving strangely.

Pilot Parker Brown is struggling to keep control.

Parker: Oh, it's acting really crazy.

Tom: Think we can see it?

Steve: I've got it.

Yeah, I can see it.

D-don't--it's quite fast.

Stop, stop, stop.

Ooh, whoa!

Oh... [Crash] [Parker groans] Oh, my God.

[Sighs] Drone down.

♪ Steve, voice-over: Even the unsuperstitious among us have an ominous feeling about this.

Something was defeating the GPS, and the drone was actually pointing itself down the gorge, so it wasn't being sucked against its will; something was causing it to want to go down there.

Ghislain: Maybe the spirits of the river, of the Nyanga kotbalungi don't want us to cross to protect us, so better to sacrifice a drone... Than ourselves.

than the person.

Heh heh!

Steve, voice-over: For our fully laden canoes, it's way too dangerous.

We're packing everything up and carrying around this lethal part of the river.

Along the way, Alessandra will rig remote cameras to discover whether chimpanzees are living here.

Steve: So today's our first day that we need to be considering animals as being a significant danger to us, uh, number one of which I think is--is elephants.

What do you think, Ghislain?

Do you think that there is, uh, any danger of-- of forest elephants here?

Yeah, there are some rules to respect.

If they charge, make sure that we stay together, and we look around.

If there is a big tree, we all go behind the tree.

Steve: I conservatively would guess we've got about half a ton of equipment to move, um, and it could be as much as 5 kilometers in distance, which is a long, long way through this.

♪ Our plan is to get back on the river in calmer water below the canyon.

We're using GPS to plot our route through the mountains.

Every step takes us deeper into unexplored territory.

♪ It's not surprising that somewhere like this is completely unknown.

[Sighs] And the potential for--for biology, for exploration is almost limitless.

[Sighs] These are called processionary caterpillars.

This is one of the most significant, uh, dangers here in the forest because they're covered in these very, very fine hairs.

They're called urticaring hairs.

It's kind of like--kind of like a stinging nettle, but the ninja version.

If you brush past any of these hairs, they get into your skin, and I've had some of these that have carried on hurting for three months after I've been stung.

It itches like hellfire.

♪ Steve, voice-over: We've been hiking for two hours, but we've barely covered a kilometer.

♪ Distance is measured in time and sweat and weight.

♪ We've been keeping our eyes up, looking for chimpanzees, but jungle guide Roger has discovered something on the ground.

So Roger's found an elephant trail, which is good because it means that the trail's going to be much clearer, and hopefully flatter, but it's bad 'cause it's elephants.

Heh!

There's the one animal you don't want to walk around a corner and see in front of you.

[Speaks indistinctly] Steve: Now, you can see the footprints of the elephants here.

It's really well-worn as they're coming in and out, and they're going over the top of this fallen log.

You can see where it's been rubbed smooth, and there's also mud here from their belly as it's grazing the tree.

Look at the size of these footprints!

That's my hand inside it.

♪ Elephants can move through the forest in almost total silence, so we must stay on high alert.

♪ [Whispering] Roger's just stopped dead.

I'm not sure what it is, but it's clearly something that's got him nervous.

Could even be elephant.

Steve, voice-over: Forest elephants can become aggressive when surprised.

♪ Ghislain: Steve: Drop your bag?

Heavy.

Steve, voice-over: Roger gives us the all-clear.

[Steve sighs] You know, you can be just a few meters off the trail, and you won't see it.

Noise doesn't travel very far in the forest.

Everything looks exactly the same.

[Insects chirping] Steve, voice-over: Elephants bulldoze through the jungle, leaving pathways behind them for other animals.

These trails are a good place for remote cameras, but there's a downside.

Alessandra: So the main challenge here in this forest are elephants because they simply get mad with the red lights of the cameras during the night.

Sometimes you are not even able to find the cameras, but just pieces all around.

[Beep] Steve, voice-over: Alessandra will leave her cameras running for a month; if we're lucky, they'll capture images of chimpanzees.

♪ Alessandra: What we are doing here is really, really important because Moukalaba-Doudou National Park was studying mainly in the northern parts of the park, so this pla-- this part of the park is complete--was-- is completely unexplored.

Nobody placed cameras out here, so each day that-- every day that we are collecting is unique, important, and can be the first step for good pro-conservation programs in that place, in this area.

♪ Steve: While Alessandra rigs her remote cameras along the elephant trail, we make camp above the gorge by a jungle stream.

These small tributaries are animal hotspots.

They come here under the safety of darkness to drink.

So Alessandra's camera traps are going to be watching day and night to see what passes close to our camp.

I'm going to try and do things the old-fashioned way, so me, Ghislain, and Roger are going to head up this way and just see what we can find.

♪ The streambeds are a thoroughfare for everything, including flying insects, and spiders know this and will string their webs to completely cover the streambed.

This one here stretches all the way out from the trees on one side, one bank, all the way to the other side, and it is exquisitely beautiful.

Look at that.

[Insects chirping] And as you're walking along down these streambeds, every few meters, you just walk face-first into one.

It's like, "Ugh!"

We'll see if we can duck underneath that one.

[Insects continue chirping] ♪ [Gasps] Oh, yes.

[Distant, indistinct chatter] Just totally, totally fearless.

Ghislain, whispering: It's my first rats, forest rats ever.

Heh heh!

I've been working in the jungle-- no kidding, 17 years now-- but this is my first forest rats I've ever seen.

Ha!

That's amazing.

Steve, voice-over: This species of wood mouse is only found in pristine habitat.

It's a sure sign this forest is healthy.

[Distant animal barks] An antelope bark echoes around the tributary.

[Squeaking] Roger calls back to attract it closer.

Can you see it?

Yeah.

Amazing!

Is that blue duiker?

Ghislain: Blue duiker.

It is so, so rare that you get a view like that of a mammal here in the forest.

Ghislain: They're very shy.

When they see you, they will just... Do you think it's not so shy because it doesn't see people?

Yeah, maybe we're the first human this duiker have seen, ever.

And to see one just wandering around in the forest, totally fearless, not fussed about us at all, you know, that's about as strong a signal as you're ever going to get that nobody ever comes here.

Heh!

How cool is that?

I'm really happy to spot one tonight.

Very, very cool.

♪ And Alessandra's camera traps have discovered the likely owner of the footprint I found earlier in the day... [Elephant huffing] but as yet, no chimpanzees.

[Birds chirping] This rainforest may be thriving, but these animals aren't safe.

Deforestation is a real threat.

Only gaining UNESCO World Heritage status will guarantee this forest and its animals protection forever.

[Flames crackle] [Indistinct chatter and laughter] Steve: 'Morning.

[Grunts] Lots of aches and pains.

[Chatter continues] Steve: We're still following the small tributary, looking for the main river.

Weighed down with all our gear, we need to find the most direct route.

♪ That sound isn't good.

It sounds like it just drops straight off here.

Steve: Yeah, I mean, this is, um, this is pretty, but you certainly wouldn't want to be carrying down through here.

What does Roger think, the best way to get to the Nyanga?

Ghislain: Yeah, he is suggesting go first and have a look down.

He's afraid that they're going to be tricky to-- we have, like, a steep place to go down with all the equipment and the gear.

Steve, voice-over: The rocks are treacherous.

There's no way we'll get the kit down them... Steve: Yeah, it's the butt slide of doom.

Steve, voice-over: but lowering the canoes down this ravine might be possible.

Tom: Maybe, if they're inflated, or inflate them on that slab, we can post them down into the pool here.

I'm going to go down, have a little look.

[Tense music playing] ♪ I can see the river.

Steve, voice-over: We've found a launch site for the canoes... but there's something even more exciting I want the team to see.

Steve: If it wasn't for this big vine running down here, you wouldn't be able to get down.

[Alessandra chuckles] Steve, voice-over: We've discovered a lost world.

Alessandra: Whee!

Ah!

Give me one of those!

Cool, man!

Ha ha ha ha!

We are privileged ones.

We are very, very privileged.

Yeah.

Very privileged.

Welcome to paradise.

Ha ha ha!

♪ You think many people have been here before?

No.

I mean, we are the first.

I'm sure we're the first.

What do you think about that, Alessandra?

You're the first person here!

Ha!

Do you really think it's possible?

Yeah, yeah.

Ha ha!

Absolutely.

Wow.

♪ Steve, voice-over: Setting foot where no one has stood before is the highlight of any expedition, and from here, we head even deeper into the unknown.

This is where the team splits.

Tom and I must drag the canoes down the ravine.

Oh, so much easier than carrying them!

Steve, voice-over: No easy task, but this tributary is the quickest way to the river.

Steve: OK!

There she goes!

[Chuckling] That's the way!

Steve, voice-over: Canoes are one thing, but there's no way we're getting the rest of our gear down the same way.

Whoo-hoo!

We decide Ghislain and the rest of the team should haul all our kits through the jungle to a calmer launch site further downstream.

[Instrument beeps] The trek will give Alessandra opportunities to place the last of her camera traps.

Alessandra: It's really hard.

The two heavy bags, so heavy.

Steve, voice-over: It's arduous, but the jungle is perfect chimp territory.

If we are quiet, we have more chance to get closer to the animals.

Steve, voice-over: However hard we try to keep quiet, our best chance of seeing animals is on Alessandra's cameras.

We can place one of these cameras that... [Beeping] now let's see.

♪ Steve, voice-over: In the ravine, I'm finding there's life in this jungle wherever you look.

It's a raft spider.

They normally rest on the surface of water, but this one's actually hunting in the waterfall.

Look at that!

That is very, very cool.

And it's a big spider, you know, almost the size of the palm of my hand.

♪ The butterflies here are incredible!

I've never seen anywhere like it!

Literally clouds of them everywhere, and they seem to be attracted to all our gear.

It's probably salts in our sweat, but they love it.

They love our bags, our helmets, our cameras.

It makes it feel even more like paradise.

♪ I don't speak much French, but I know enough to know that I'm going to call this "le gorge de papillon."

Ha ha ha!

I like that.

Yeah.

Butterfly Canyon.

♪ ♪ Steve, voice-over: Tom and I face powerful rapids to meet up with the rest of the team and all of our kit.

[Suspenseful music playing] ♪ Steve: Whoa, that's a big boil!

Tom: Yeah, it's a big boiler.

Really big boil.

This river's full of 'em.

♪ Steve: Whoo-hoo!

Throws you, doesn't it?

Tom: All right, this is good.

♪ Big wave!

Hee hee hee!

♪ ♪ Whoa!

Whirlpool, whirlpool!

♪ [Music intensifies] ♪ Taking on a lot of water here.

Yep.

It's not an easy river, this.

It is not an easy river.

♪ [Instrument beeps] Steve, voice-over: After two long hours of paddling and jungle-hauling, the team reunites.

From here, we'll head deeper into the unknown zone, using the river as our jungle highway.

[Thunder rumbling] [Loud rainfall] Proper, proper rain.

See... Steve: Is that right?

We are blessed?

Yeah.

I don't feel blessed.

I just feel wet.

Ha ha ha!

This river is going to react to this kind of rain, and it will come up, the water levels will come right up.

[Sighs] Steve, voice-over: While Alessandra checks out the forest around the launch site, Tom and I trek back to fetch the last of the canoes.

Everything you own is soggy.

Uh, changes the whole experience.

[Pants] But then, you know, you're in the rainforest.

You can't exactly win, can you?

Heh heh heh!

♪ Steve: Yes!

Come on!

♪ Steve: Whew!

I am knee-deep in water here.

♪ Oh, that has been a big day.

Steve, voice-over: Finally, we've got the whole team and all our equipment back in one place.

Steve: We're back on.

Yeah.

We are back on!

Wow.

Cool, mate.

Steve, voice-over: And in the jungle, Alessandra has struck gold.

I have a nest!

Let me see.

I can see just one.

Steve: What kind of nest?

Chimps!

So we have a result.

I found something.

Heh!

Steve: That is a proper nest, right there!

Alessandra: Yeah.

Whoa, that's amazing!

And these are fresh.

So we have two chimp nests.

They are relatively fresh.

We can take GPS point about it, create a map if we will find other traces.

Anyway, we can for sure say that here there are chimps.

For the whole idea of trying to make this into a World Heritage site... Mm-hmm.

that was one of the most important things...

Exactly.

that there are chimps here.

Yes.

And now we know there are.

Yeah.

Yeah!

That's great news!

So now let's take a GPS point.

We can make some picture of these nests, and, uh, we have our data.

Steve, voice-over: Evidence of fresh chimp nests is an important find.

If Alessandra's camera traps can capture footage of the animals, we'll have vital evidence to present to the government of Gabon.

[Instrument beeps] The cameras will be left running for weeks and collected once the expedition is over.

For now, it's time to get back on the water, but after the turbulence of the canyon, we're wary of what the river may throw at us.

So everything that's going into the boat has to be lashed in tightly 'cause there's every chance one could go over, and if they do, all of this goes in the drink and is gone.

[Woman vocalizing] Steve, voice-over: Capsizing is the last thing we need.

Our guide Roger warns there are crocs in our river.

[Speaking French] Four?

Roger: Right.

Four-meter-long Nile crocodiles.

That's a pretty good reason not to take a swim, isn't it?

[Speaks French] Steve, voice-over: Now we're beyond the canyon, we can check out the rest of the unknown zone.

Ahead of us lies a 30-kilometer stretch of unexplored river and jungle.

Our goal now is to break off the main river into quieter tributaries.

♪ I spot an opening in the trees.

♪ It's exactly what we've been looking for.

♪ [Insects chirping] This is magic.

Uh-huh.

Ooh.

♪ Steve, voice-over: The route is littered with water-soaked and fallen trees.

♪ Some we can go around.

Others need shifting.

I don't want to spoil the silence.

[Water sloshing] Ooh, that's a strange sensation.

Look at that.

[Blows raspberry] Tom: Well, you can just--oh, there you go.

Alessandra: You're surfing it.

Ha!

Wild.

Heh!

You're riding the log.

That is completely wild.

You're riding the log.

Ha ha ha!

Aah!

In.

In and through.

Ha ha ha ha!

Well... Oh, that's-- you know, it's all about improvising, isn't it, jungle travel?

Heh heh heh!

♪ Steve, voice-over: Our canoes allow us to move silently.

We can spot animals before they spot us.

♪ In tributaries like this, we can take our time and witness jungle life without abetting it.

♪ Alessandra has specialist sound-recording equipment, which will pick up primate calls from miles around.

She can identify each species from its call.

[Distant barking] Alessandra: Steve, voice-over: Movement in the canopy catches our eye.

[Whispers] Moustached monkey?

Alessandra: Moustached guenon.

Steve, voice-over: The moustached guenon is barking a warning.

This is his territory.

Alessandra: Yep.

Steve: Amazing jumpers.

They almost look completely weightless.

[Monkey squeaks] Steve, voice-over: Spotting two species so close together is perfect; this rainforest is truly special.

Steve: Wow.

Absolutely unbelievable.

♪ [Softly] There's a pygmy kingfisher.

I'm absolutely speechless.

Kingfishers are usually so flighty and won't let you get close.

This one is sitting four meters away from us?

You know, you just--you never get kingfishers this fearless.

♪ Steve, voice-over: The further we explore, the shallower the tributary becomes.

Steve: There's a huge trail coming down to the side of the river here, where the elephants cross and we're starting to get into very shallow water, where we're having to get out and walk, and that does make us quite exposed.

If we were to encounter elephants here, we wouldn't be able to get out of the way, um, and I think, pretty soon, we're going to get to a place where we can't paddle on any further.

What's the plan now?

Just trying to get a GPS fix now, which is obviously quite tricky through this thick canopy.

We're right in the middle of the jungle now.

From here on in, we could well be dragging, and dragging a lot.

There's huge amounts of elephant sign... Mm-hmm.

and we're very vulnerable sat here, you know, unable to move in the boats.

Steve, voice-over: As we lose daylight, we return to deeper water to make camp.

Awesome, yeah.

Nice work.

Good guns.

My hammock's supposed to have a--like, a tent pole that goes over the top there to get the, uh, mosquito net clear over your head, but as we've been trimming down to save weight, I've just been making one out of sticks every night.

♪ Steve, voice-over: I'm not ready for bed just yet.

Nighttime is when the jungle's predators come out to hunt.

♪ [Distant animal calling] ♪ Ghislain: Ghislain: A big one.

Yes, a really good size.

They don't get much bigger, do they?

[Splashing] Steve: Whoa!

Almost jumped into the boat!

[Chuckles] I was very nearly sharing our canoe with a good-sized crocodile.

Steve, voice-over: And this croc is not alone.

♪ Despite the size, they're very, very strong.

In fact, pound-for-pound, this would have to be one of the strongest of all crocodilians.

This one here is a good few years old, and it's going to be feeding on freshwater invertebrates, probably on small fish, and it's kind of a king of this environment.

To see this one here--happy, hunting, healthy--is just another sign of quite how healthy Moukalaba-Doudou is.

♪ Steve, voice-over: It seems, wherever I step, there's another species of croc looking for its next meal.

Just come down to my hammock and seen a couple of, um, crocodiles in the water right next to where we're staying, um, and I assumed they were the common ones that we've been seeing, the dwarf crocodile, but they're not.

They're a--a completely different species.

Steve, voice-over: It's a slender-snouted croc.

It's such a remarkable-looking crocodile.

The "slender-snouted" name comes from the fact that the snout is long and very, very thin.

That means it can cut through the water really easily.

It's not got any drag, so it's really good for catching fish while they're underwater.

Wow.

No.

I mean, to some people, that might be just a crocodile, but to me, that is an incredibly significant discovery.

I've been here in Gabon, out for night upon night, trying to see one of these things and never succeeding.

They are so rare.

Critically endangered animal.

Steve, voice-over: This hidden corner of Gabon has been full of surprises for all of us.

Ghislain: When you open up yourself to nature, nature will open up to you.

[Roger speaking French] ♪ Steve: With all of Alessandra's cameras now watching the jungle, it's time to move on, but our expedition is far from over.

Between us and our exit, 20 kilometers away, is a worrying section of unknown and unrun rapids.

Tom: I feel like this is the last obstacle, you know.

This has been a really... ambitious expedition in quite a challenging environment.

Ghislain: Yeah, true.

Tom: So this last section of rapids is our last hurdle, our last obstacle.

We'll be OK, Steve.

Trust me.

I trust you.

You trust me, yeah?

But we'll-- Steve: You used the word "trust" three times in one sentence there.

[All laugh] That tells me you're thinking something completely different.

Ha ha ha!

Try to laugh.

[Both laugh] [Insects chirping] Steve: 8 a.m.

Sweaty, dirty, itching from mosquito bites.

Situation: normal.

Steve, voice-over: Today we leave the unknown zone.

Tom McLay prepares us for what lies ahead.

[Suspenseful music playing] Now we talked about it, but there are going to be some rapids downstream a bit.

Some of these are going to be very similar to what we saw on the first day, but some of them are going to be longer and more significant.

[Speaking French] Steve, voice-over: Ghislain makes radio contact with park headquarters, who are waiting for us at our endpoint downstream.

From satellite imagery, we can see the 20 kilometers we have left looks like a steep descent, so we're bracing ourselves for a bumpy ride.

3, 2, 1.

[Grunts] You can hear the rumble of that whitewater already.

Tom: Oh, so just follow me, guys.

[Suspenseful music playing] Steve, voice-over: Tom and cameraman Graham go first, followed by Alessandra and me.

Alessandra: Oh, my God.

♪ Steve: Good work!

Really good work, really good work!

Steve, voice-over: The rapid is taking us into a gigantic, swirling boil.

Keeping the canoe upright is all about timing and teamwork.

Steve: OK, it's fine.

♪ How you doing, Alessandra?

Yeah, it is down, no?

I am fine, thanks.

Quite tired, but I am down.

Ha!

It's fun.

It's good down there!

Ha ha!

Steve, voice-over: Ghislain and drone pilot Parker are dragged into the same whirlpool.

Oh, whoa, whoa!

[Suspenseful music playing] ♪ Steve, voice-over: But they're not so lucky.

♪ Hold on.

I've lost my paddle.

OK, I'll get it.

Steve: He may be able to self-rescue.

♪ Tom: Let's flip this boat over, guys.

Come on.

♪ Steve, voice-over: It's a shock, but they're safe... OK, let's go.

and the lashed-down equipment means nothing's been lost.

♪ We're drawing closer and closer to our endpoint, a spot where we can all take out, and everyone's got into the rhythm of it and they're doing really well.

♪ Steve, voice-over: But it's no time to relax.

The more extreme rapids are just ahead.

Tom: From here, you can see the takeout.

You guys are going to stay here, we're going to go down.

Steve: All right.

Steve, voice-over: Tom has been gone for 20 minutes, and he radios back.

Tom on radio: Steve, voice-over: With our endpoint almost in sight, we've radioed ahead to alert the next village in the national park.

They've stationed safety boats below the rapids.

Steve: OK, guys, so I'm going to go first.

If everyone tries to follow my line, but keep behind, like, three boat lengths, ideally.

[Rousing music playing] ♪ Ah!

OK, now we want to be off-center.

Whoa!

Ha ha!

It's OK, it's OK!

Don't worry!

It's all good!

♪ Whoa!

Ha ha!

We're all heading for a huge standing wave.

♪ Whoa!

Oh, my God!

Stop!

♪ Steve, voice-over: We're sucked under for close to half a minute.

♪ You OK?

Uh, yeah.

[Grunting] Look, can we turn the boat this way?

[Grunts loudly] OK!

Oh!

OK, I'm coming to help you!

♪ Steve: 1, 2, 3!

[Grunting] That's it.

You're in.

Yeah, yeah, I'm fine.

OK?

Where'd that paddle go?

I'm fine.

[Panting] Was very scary.

So we have no paddle, so we will probably go in again.

♪ ♪ Steve, voice-over: The safety boats waste no time extracting us.

♪ Well, I'm not going to lie.

That was hard-core.

Alessandra, laughing: We made it, Steve.

Ghislain: We made-- we made it!

We made it, we made it.

Yes!

We made it.

Whoa!

[All laughing] Yes!

Steve: Well, that was more full-on than I think any of us were expecting.

Uh, every single one of us went down the rapid, uh, upside down, underwater.

Couple of the guys got sucked into whirlpools.

It just went straight down, um, and, uh, it's pretty intimidating.

I'd say it is intimidating in that water, but we're here, we've done it, we're finished.

Alessandra: Oh, my.

We made it.

We did.

We made it.

Oh!

Good job.

Well done, well done.

We are here.

I am so proud of me and of my partner of the entire trip.

Yeah.

You done good.

Yes.

You did really, really well, and thank you for bringing me here, man, thank you.

It's been a very, very special trip.

Very special trip.

Was a pleasure to be here with you, um, and I hope that the rest of the world will, uh, yeah, see how beautiful and amazing country we are here... Steve: Yeah.

especially this particular spot we've been through these last days.

Steve: So how does it rate on all the trips you've done here?

Uh...it's definitely coming at the top, top, top, top of all the trips I've done in 17 years so far, so far, yeah.

Got quite hairy in there for a little bit.

I'm so--quite glad that you were in control of safety and not me 'cause I was swimming.

It's hard for anybody to get through that unless you're in a big raft.

Ha ha ha ha!

He thinks it's the first and the last time this will get done.

[All laugh] Steve, voice-over: I'm not a superstitious person, but I felt the power of this rainforest like nowhere else I've ever been, and I've been working in the forest in this part of Africa for years now, and yet that sense of the total unexpected, of not having any idea of what's going to happen next is what has made this expedition just utterly remarkable.

Steve, voice-over: One month later, Alessandra's camera traps are collected.

The footage of primates is stunning: a beautiful white-collared mangabey; and at last, footage of chimpanzees.

It's a big step forward to help Moukalaba-Doudou achieve the World Heritage status it so desperately needs.

♪ This little piece of paradise is under so much human pressure and yet, still, there are places as perfect, as pristine as Moukalaba-Doudou.

♪ We need to protect this place.

♪ It's essential for the future of the wildlife and the forests, but also for ourselves.

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

[Majestic instrumental music playing] ♪ ♪ ♪