The Amazon, the Earth's mightiest river.
For the last month an expedition has been exploring the alien world beneath its surface.
Now the team is prepared for its greatest adventure.
To explore the Amazon's abyss.
Nobody knows what lurks in its hidden depths.
Solving the mystey will be their greatest test yet.
It's the final week of the expedition.
Storms of the rainy season have arrived.
River conditions will soon be too severe for diving.
Time is fast running out.
They're facing the most difficult challenge yet
the expedition's ultimate goal
to find life in the abyss.
Now 1000 miles from the sea, they are nearing the deepest point of the Amazon.
During the last 4 weeks, they've made over 60 dives to the river bed.
A bizzare underworld, with creatures adapted to a life in murky water.
Some armored to fight back,
but going deeper is frought with dangers.
3 weeks ago the divers descended to 45 meters.
It was so dark, they could hardly see, far less find life.
In such conditions the risk of sending divers to 90 meters is just too great.
To achieve their mission of filming life in the deepest abyss,
The expedition has just taken delivery of a very special piece of kit.
For cameraman Mike DeGruy, it means they have a real chance of success.
Kate Humble helps unpack the expedition's new toy.
This is an ROV , a remotely operated vehicle.
With it they hope to make scientific history.
This goes way deeper than any of us can go.
We can take this and place it into a spot, and can stay down 24 hours a day
as an eye in the river.
We've got 2 cameras, we've got a sonar, we've got lots of instrumentation
that we can put on and take off.
This is a very cool toy. To be able to get a view
of the river that we would never be able to get as diver, is great.
And the other thing is that it doesn't run out of air, it can be down there all day.
They want to fly the ROV far beyond safe diving range.
To help, they're joined by Steve Sargison, specialist ROV pilot.
He's spent his career salvaging wreks.
Forwards, backwards, go left, go right
that will give us full power, that will give us full power when down, and this is a fine trim.
The river current runs at 3 knots.
The ROV will only be just able to cope.
Any equipment failure could be desastrous.
The river bed here plunges to more than 90 meters deep.
This is the moment scientist dr. Mario dePinna has dreamt of for years.
We are here, taking the opportunity of coming to these remote places
but really the new stuff, the extraordinary stuff, is found in deep water.
The ROV's first flight reveals a problem.
One of the motors has failed.
Without full power , the ROV cannot descend.
Unless the engine could be fixed, the abyss will remain tantalisingly out of reach.
The robot is operating at its limits in a river so deep
it's a major shiping channel, right into the heart of the jungle.
Steve needs to get to grips with the ROV
Time is now precious.
The team grab a last chance to explore places that will soon be washed up by the rains.
Mike Pitts is going to look for fish on the forest floor.
Further down river, Kate and Mike investigate an area of jungle that is underwater.
To get steady images of this drown jungle, Mike improvises a novel form of propulsion.
Every year, vast areas of the forest are flooded.
The trees and the wildlife are perfecly adapted to survive the inundation.
Fresh water sponges cluster in the branches, waiting to be immersed.
And fish spill out across the forest floor.
Mike Pitts is looking for fish that will be high and dry until the floods are off.
This jungle has been above water for 3 months.
Mike's team is joined by a local scientist
who's recently discovered unique fish on the forest floor.
Any fish here were trapped in pools by a retreating river.
and must endure months in stagnant waters, before the flood returns.
Some are so small they can only be found with a fine mesh net.
Is that a fully grown specimen ? No, it's a juvenile.
Juvenile ? They grow up to half a meter...
Half of meter ? Yeah
And it bites ? Painfully
I think I'm gonna release that.
But weather permitting, they hope to find an even more remarkable fish.
On a journey up here someone is explaining to me
about a small catfish, wich , is probably blind
but lives in these very shallow waters, or even in the soil.
It looks like a worm, but it's actually a fish, it's got feelers, it's got the whole thing.
Yes, that's a fish, look at that.
It's totally red That's the worm--
or the catfish. I think it's a large one.
If I'd find that by myself I wouldn't noticed that this isn't a worm
That's no way I would say that is a catfish.
This fish has no name. It's a new species.
And I've got it in my hand
The whole of its body can absorb oxygen from the air.
A miniature catfish that can live on land.
It is taken all day to fix the robot, and they are well behind schedule.
As night falls, they launch a deep water test-dive.
This is the first ever attempt to reach the abyss.
But there's trouble brewing.
It's gonna become a hazardous situation for the equipment
so I hope the storm won't come
But if we are gonna stop doing things just because of the storms, we'll never do anything
because there's a storm threat in the horizon every 10 minutes.
Suddenly the storm changes direction.
This is weather that can sink ships.
Until they get the ROV back on board, they're stuck directly in its path.
It seems the Amazon is conspiring against their mission.
So much electricity going on up there
It's impressive, and you can see
a different kind of splendor in the Amazon.
Next morning there's a break in the weather.
The robot is launched and descends into the unexplored depths.
At last they are poised to find out if there's anything living in the abyss.
They're using a bag of fish bait, to attract predators from the gloom.
Scientists know the Amazon is rich with life to a depth of 30 meters
but the ROV is already well below that.
6 minutes, we have the first fish.
two of them now.
They've got tiny, tiny eyes
and big sucker mouths
The bait is working.
The first sign of life deep in the Amazon.
There's five of them
It's getting kind of busy. Look at that !
For Mario, a major breakthrough.
These are scavenging catfish.
We have never seen this spectacle before, this is the first time I see it.
Wonderful. They have huge muscles
the jaw muscles are so big, that they actually cover
their whole head, all the way to their midline
and that's a very vey powerful bite.
These guys can use a little hole to get inside and eat.
That kind of scares me more than just having a piece of flesh taken away.
These scavengers feed on the dead, but can attack the living.
With a ring of teeth like a ripping circular saw, candiru bore into flesh.
Fish that thrive at 44 meters.
But does anything exist in the deepest abyss ?
They may yet be thwarted
The ROV has badly malfunctioned.
Steve is forced to do electrical surgery.
It's going to take some time.
Next morning, with the further delay,
and just 2 days of expedition time left,
Mike grabs a chance to fulfill a personal ambition.
His search takes them far into the jungle,
with amazon guide Samuel.
They're looking for a sloth.
It's really hard to find them, because they grow in the trees, and stay over there.
They don't move there much
If only we can find one of these things, because I realy want to see a sloth before I leave the Amazon.
The fact that they move so slowly, and they are covered with algae and so well camouflaged
makes them practically impossible to spot.
This is ideal habitat for sloth.
But it will soon change out of all recognition.
In the coming months a deluge of rain will flood the jungle.
The interesting thing is it all happen without ever raining here.
The rains are by the Andes, or somwhere else,
and the river just lifts up anyway.
Every year...that is a lot of water.
But the sloths will remain high in the canopy, above the raising water.
It takes an experienced eye to spot one in its lofty retreat.
Right in front of us there's a sloth.
I don't belive it.
More than anything else, I love the way they look and move.
I wonder if they make decisions at the same pace they climb.
See, I don't know
why I have this obsession about seeing a sloth while I'm here,
but certainly the sloth's unique, and... I saw myself
Mike has realised his life-long ambition.
The expedition main objective is proving harder to achieve.
The robot has been repaired.
It's already been underwater for an hour, and it's reached a depth of 80 meters.
The deepest they've ever been.
But the visibility is almost zero.
They have no idea what obstructions are hidden ahead.
We're inside this shipwreck.
See the metal structure there ? Yeah.
So we need to not move, but think about how we do this.
By extraordinary chance, they've stumbled into the bow of a sunken freighter.
The river is deep enough to swallow a ship without trace.
The slightest mistake, and the robot will be lost forever.
Steve follows the ROV's ombilical to find the way out.
But runs into another obstruction.
Stop. Stop.
It looks like I've managed to get 20 meters up
out of the shipwreck, but now we're probably stuck
In these currents, it will take all Steve's skill to retrieve the robot.
Ok, I think we're free now.
The team's deep water quest has been saved... but only just.
One hour later, they're ready to go again.
Fresh bait is secured, and quality tested.
The have only 2 nights left,
and storms could shut them down at any time.
The boat has been moved to avoid the wreck.
They must quicly launch into the abyss again.
The robot is primed for its deepest dive yet.
It's descending smoothly, dropping down towards the river floor, far below.
No camera has ever pried this deep into the Amazon before.
This is in a river ! This is in the middle of the Rio Negro ! 250 feet. Unbelivable.
To increase the chance of attracting fish in the greatest depths,
they have switched to a low-light camera.
Now all they can do is wait.
For 5 hours, nothing.
Then, suddenly, from the darkness, the ghostly images of candiru azul appeared.
This is the first time anyone sees images of fish at 85 meters deep.
There is life in the abyss after all.
When did you know that candiru will eating and feeding at 85 meters ?
No, I didn't expect that life below 30 meters will be that rich.
A relative of the candiru azul, but larger, and even more voracious.
That did not looked like the same ones we've been seeing. That's a different candiru azul.
That's really different. The little ones are gone.
It's a beautiful fish, it's silvery, it has a long dorsal fin
There it is again-- Comes, grabs a big chink of flesh, and swims away.
It doesn't staying around and trying to grab it--
That is great
Wow, there's two of them
--takes it and goes.
What is really surprising me is just how fast all these fish we've seen are moving at these depths.
They've revealed that the abyss swarms with life.
Scavengers waiting for anything the river brings them.
These images are something really original.
It's the expedition's final day.
To get better pictures, the team decide to risk sending in the divers
with their high-tech cameras.
They're on the very edge of the abyss.
There's a narrow shelf within diving reach.
But is it in the candiru azul territory ?
No one has gone face to face with these voracious scavengers before.
The divers are preparing for an encounter that could be dangerous.
One bite, and you start bleeding quite profusely,
that could attract the others, and before you know, you got a situation on your hands, and you got to get out of the water quick.
If the bait attracts candiru azul, once in the water, there will be no going back.
Thunderstorms threaten nearby
If they come much closer, they may have to abort the dive.
After 40 minutes, there are still no candiru azul.
Is it to shallow after all ?
They're unbelivably energetic
It's allmost like they figure : This meal isn't gonna last long, I better take it while I can.
Nearly blind, candiru azul tracks its prey by scent.
It's treamline body allows it to rife (???) , gourging inside its victim.
So, are they eating from the inside out ?
It looks like maggots. Yes I would say they are eating it from the inside out.
Oh my god, they're going after my stomach now.
They're getting too close for comfort now.
Perhaps only their wetsuits are saving the divers in waters infested with candiru azul.
Although the reputation of the piranha is legendary,
could it be that these are the true monsters of the Amazon ?
I'm just glad that these are just scavengers, and not predators,
because I can't imagine that piranha are any more aggesive than the candiru.
The weather topside is deteriorating fast.
i'm gonna leave now, and I'm gonna go back up
This is been quite an experience, and I want to remain a good one.
Ok, Mike, we will see you on the surface, everyone here is standing by...
Holy cow, if I had known about that when I first came here
I would have worn chain mail every day.
It was quite dramatic, and I've done many dives all over the world
and I think that has to go down as the most disturbing.
They have good reason for their concerns.
Candiru azul are tenacious to the extreme.
They continue to devour the bait, even when it's back above the water.
The expedition is nearly over.
In 5 short weeks, the 50 team members have voyaged 3000 kilometers.
They've experienced the incredible variety of Amazon's wildlife first hand.
Over 100 species have been filmed, many for the first time
They've discovered fish completely new to science.
But all this is only scratching the surface.
There are thought to be another 2000 species still to be recorded.
In this eerie world of the strange
who knows what extraordinary creatures may yet be found.