0:00:03 > 0:00:05The Amazon - a wilderness teeming with wildlife.
0:00:05 > 0:00:11But one part is still totally unexplored - under the water.
0:00:14 > 0:00:18Hidden in the river lie some of the fiercest and strangest creatures on Earth.
0:00:18 > 0:00:22Man may have walked on the moon, but no-one has journeyed
0:00:22 > 0:00:25to the very bottom of the Amazon.
0:00:25 > 0:00:27Until now.
0:00:27 > 0:00:32An expedition is searching for the animals hidden in the depths.
0:00:32 > 0:00:35We're looking in places that no-one has looked, we have the ability
0:00:35 > 0:00:38to see and film things that no-one has ever seen.
0:00:38 > 0:00:43We've not just scratched the surface of the Amazon, but we've gone beneath
0:00:43 > 0:00:47it and we are bringing back stuff that is gonna make people go "wow".
0:00:47 > 0:00:53But the world's greatest river doesn't give up her secrets easily.
0:01:04 > 0:01:10Manaus, in the heart of the jungle, bristling with sailors and river traders.
0:01:10 > 0:01:15It's Day One for our explorers.
0:01:15 > 0:01:18They're some of the most experienced divers in the world
0:01:18 > 0:01:21but they're going where no-one has ever dived before.
0:01:23 > 0:01:26For the next five weeks this boat will be their home.
0:01:26 > 0:01:29Their mission - to take BBC cameras to this last
0:01:29 > 0:01:34great unexplored habitat in search of unique creatures of the deep.
0:01:34 > 0:01:38The diving's led by Mike deGruy - professional cameraman,
0:01:38 > 0:01:41veteran of The Blue Planet and a hundred other wildlife films.
0:01:44 > 0:01:48We really are on a wonderful expedition, we have the opportunity to take all of this
0:01:48 > 0:01:53gear and film things nobody's ever seen, nobody's ever heard of, and we're really gonna do it.
0:01:53 > 0:01:58Also on the dive team, explorer and naturalist Kate Humble.
0:01:58 > 0:02:01Just the most beautiful boat,
0:02:01 > 0:02:03I feel like I'm about...
0:02:03 > 0:02:06to take part in "African Queen".
0:02:08 > 0:02:11Their challenge is formidable.
0:02:11 > 0:02:14The Amazon hides its creatures in waters so dark
0:02:14 > 0:02:18that no explorers have ever succeeded in penetrating its depths.
0:02:32 > 0:02:40Their journey will be through the richest rainforest on the planet - a jungle where a million species hide.
0:02:43 > 0:02:46But their adventure will take them to the Amazon
0:02:46 > 0:02:52no-one has seen before - beneath the surface of this immense river.
0:02:54 > 0:02:594,000 miles long. In places wider than the English Channel.
0:02:59 > 0:03:03It would take 100 years to explore the 5,000 tributaries -
0:03:03 > 0:03:06they have just one month.
0:03:06 > 0:03:10The multi-national team of scientists and divers will have to overcome storms and setbacks
0:03:10 > 0:03:19to discover species new to science, film underwater giants, and track down primitive flesh-feeding fish.
0:03:24 > 0:03:31Their 2,000-mile journey will ultimately lead them to dive a black hole in the heart of the Amazon
0:03:31 > 0:03:36where with underwater robots they hope to find creatures hidden in the abyss.
0:03:39 > 0:03:42I'm Kate...
0:03:42 > 0:03:47- Kate.- Kate's an experienced diver but like the rest of the team it's her first time in Brazil.
0:03:47 > 0:03:49Says Kate on the door.
0:03:49 > 0:03:55This is really gonna be my first rainforest experience and, um, and
0:03:55 > 0:03:59all you hear about is the enormous numbers of diseases that you can get.
0:03:59 > 0:04:05Mike's made more than 5,000 dives in every corner of the planet.
0:04:05 > 0:04:08As far as difficulty is concerned, this ranks right up there,
0:04:08 > 0:04:11other areas like Antarctica, under the ice has its own set of problems,
0:04:11 > 0:04:16- but these are unique problems. - Everything kind of falls apart, nothing heals up properly,
0:04:16 > 0:04:21you know, one little snag on your finger will mean that your finger will probably have to be amputated.
0:04:21 > 0:04:24On a good day, the visibility is terrible,
0:04:24 > 0:04:30we don't know where we're going, we have no reference material, and divers in this area, plus,
0:04:30 > 0:04:33there are animals down there that could kill you.
0:04:34 > 0:04:37The anaconda
0:04:37 > 0:04:40grows to over nine metres long.
0:04:40 > 0:04:44And the caiman, weighing in at a quarter of a tonne...
0:04:46 > 0:04:50Over the next month, the divers will come face to face with both of them.
0:04:55 > 0:04:59The expedition has two local guides who know the risks better than anyone.
0:04:59 > 0:05:05Samuel Basilio and Eduardo Gomez are briefing the divers.
0:05:05 > 0:05:12Anacondas maybe just break your leg or arm, or your body, easily.
0:05:12 > 0:05:13They may kill you.
0:05:13 > 0:05:19I recommend that everybody buy and have a knife - a very sharp one.
0:05:19 > 0:05:22Don't be too confident when you get in the water, cos that's when the big
0:05:22 > 0:05:26accidents happen in the Amazon, even with us.
0:05:30 > 0:05:38You have to assume that an animal that has evolved in water this murky has evolved a way of detecting
0:05:38 > 0:05:41a 6ft body down there.
0:05:41 > 0:05:45So you know in the back of your head that they know you're there.
0:05:45 > 0:05:46You don't know they're there.
0:05:46 > 0:05:49And that puts them at a big advantage.
0:05:49 > 0:05:51And I don't necessarily like that.
0:05:51 > 0:05:59My head says, of course there are risks, and play it carefully, but my heart says, great.
0:05:59 > 0:06:03I just want to do it. I'm not thinking about - is it dangerous?
0:06:05 > 0:06:10There are three boats on the expedition - one for living,
0:06:10 > 0:06:15one for support and one for diving.
0:06:17 > 0:06:21Their first mission is to travel to a remote tributary of the Amazon -
0:06:21 > 0:06:23the Rio Ariapiuns.
0:06:23 > 0:06:27The scientists believe that it's home to many rare species.
0:06:27 > 0:06:29Even if you do that, I still can't...
0:06:29 > 0:06:33As they draw near to their destination, every second is spent preparing the equipment.
0:06:33 > 0:06:36Safety is everything.
0:06:36 > 0:06:40Most important of all, they must be able to talk to each other underwater.
0:06:40 > 0:06:43It could save their lives.
0:06:43 > 0:06:48Every single person underwater can talk to each other as well as talk
0:06:48 > 0:06:53to the boat, which is where Mike will be with our topside comms unit
0:06:53 > 0:06:57and he'll be able to talk to us, and we'll have great communication,
0:06:57 > 0:07:02and I personally feel that that communication is the key to the safety of this operation.
0:07:12 > 0:07:15The expedition has reached the first dive site.
0:07:15 > 0:07:22The whole team has focussed on the preparations and the gear has been checked and checked again.
0:07:22 > 0:07:25In these conditions, there's no room for error.
0:07:34 > 0:07:36The air is clammy and hot.
0:07:36 > 0:07:38The river will be just as warm.
0:07:45 > 0:07:50The aim of the dive - to discover just how much can be seen underwater.
0:07:55 > 0:07:58It is a step into the unknown.
0:08:11 > 0:08:15Despite the heat, for their own safety, they must be covered from head to foot.
0:08:17 > 0:08:22There's no way I'm not going in without all this protection, having heard what there is in there.
0:08:22 > 0:08:24Right.
0:08:44 > 0:08:48As they descend, the divers discover a different world.
0:09:07 > 0:09:12The water is heavy with sediment and they quickly lose sight of one another.
0:09:23 > 0:09:28Anything could be swimming past them, and still not be seen.
0:09:58 > 0:10:02The state of the art diving gear allows them to stay in the water until night is fallen.
0:10:02 > 0:10:05But they still haven't seen a single creature.
0:10:05 > 0:10:08Are you all right, Kate?
0:10:08 > 0:10:13It was so murky, I had a torch held to my computer,
0:10:13 > 0:10:15and I couldn't see the display.
0:10:15 > 0:10:21You can't help but think these animals have developed a way to sense through the murk,
0:10:21 > 0:10:27there would be no reason for us to know how to do that, we don't live in a situation
0:10:27 > 0:10:31where the farthest thing we can see is 15 inches away from us - they do.
0:10:31 > 0:10:36If you can see anything down there at all, then that camera's a miracle.
0:10:36 > 0:10:39It's a miracle.
0:10:39 > 0:10:42The team are in sombre mood.
0:10:42 > 0:10:46No-one suspected the visibility to be quite so terrible.
0:10:46 > 0:10:51The whole future of the expedition is in doubt.
0:10:56 > 0:10:59But there's no giving up.
0:10:59 > 0:11:03First thing next morning, the boats push further up the river
0:11:03 > 0:11:06and into the unknown in search of better sites.
0:11:08 > 0:11:14The diving will be dangerous. The job of keeping everyone safe rests
0:11:14 > 0:11:17with dive marshal Richard Bull.
0:11:17 > 0:11:21In all the hair-raising deep adventurous diving I've done,
0:11:21 > 0:11:24this is some of the most challenging I've ever come across.
0:11:24 > 0:11:31We have great expectations piled on our heads to deliver unique images, OK - well, I'll buy, I'll take that
0:11:31 > 0:11:37challenge on, but what it means is we've got to go to different places and dive and dive and dive.
0:11:43 > 0:11:49Powerful lights and high definition cameras are being used to cut through the murky Amazon waters.
0:11:49 > 0:11:53But high-tech gear brings no protection from predators.
0:11:53 > 0:11:58Mike Pitts has spent his career filming the creatures of the deep.
0:11:58 > 0:12:03I think if you can see something from a distance, you don't think half as much about it, it's when you have
0:12:03 > 0:12:06that very limited visibility and they're on you before you
0:12:06 > 0:12:09could even do anything about it, it's like you can see a tiger shark
0:12:09 > 0:12:16from 30 metres away and you're happy, you're fine, you can face it off, but in this low-vis, it is a worry.
0:12:16 > 0:12:22Professional divers train to stay calm in the face of danger and keep their fear firmly under control.
0:12:22 > 0:12:28I'm not going in the water feeling 100% happy, but once you have a camera in your hand, you're checking
0:12:28 > 0:12:31your focus, you're checking the lighting, you're communicating
0:12:31 > 0:12:36with your buddy, if you let yourself start thinking about it too much, you'll always be looking over your
0:12:36 > 0:12:42shoulder behind you and I'm sure we are gonna get moments where we get bumped by things down there.
0:12:44 > 0:12:49- But people who have spent their life by the river are not so relaxed about the dangers.- I have to
0:12:49 > 0:12:54be sure that nobody gonna be hurt by anything
0:12:54 > 0:12:59and I know that's my...my job is to protect all the crew.
0:12:59 > 0:13:03I spent all my life fishing, I've been in contact with the
0:13:03 > 0:13:08stingrays and snakes and electric eels - I mean, they're really bad.
0:13:10 > 0:13:16Every year, local people are attacked and killed by underwater predators.
0:13:16 > 0:13:18The divers are not immune.
0:13:18 > 0:13:24The teeth of the red-bellied piranha are razor sharp and can easily slice through a wet suit.
0:13:24 > 0:13:30The electric eel will discharge 600 volts if disturbed, leaving a diver unconscious.
0:13:30 > 0:13:33But for the people of the Amazon, there is
0:13:33 > 0:13:35another creature feared even more -
0:13:35 > 0:13:41it lives in the depths of the river and has never been filmed...
0:13:41 > 0:13:45The giant jau.
0:13:45 > 0:13:47The jau will not come to swallow men,
0:13:47 > 0:13:51but maybe if they're in a school of fish, try to grab something -
0:13:51 > 0:13:58maybe they get scared and, hit someone with their head, and, or swallow leg, pull you down
0:13:58 > 0:14:01and this will be dangerous for sure.
0:14:01 > 0:14:06They, they bite, you know, they don't have sharp teeth but they have
0:14:06 > 0:14:10a big mouth - you know, when they're very big, they can swallow anything.
0:14:10 > 0:14:15Three friends of mine they jump and they then decide to go swimming to the shore
0:14:15 > 0:14:21and one of them disappeared so, we never found his body, never.
0:14:21 > 0:14:28The giant jau has a terrible reputation for dragging fishermen down into the depths, drowning them.
0:14:28 > 0:14:34Reports have come in to the expedition team that jau have been found further up river.
0:14:34 > 0:14:37We heard from the village cos we've got some contact with this village,
0:14:37 > 0:14:41that they caught two jau catfish there, about a week and a half ago, so we
0:14:41 > 0:14:47- should see a big fish.- Can we expect to actually find one under a ledge and we can get relatively close and
0:14:47 > 0:14:51- he's not gonna leave?- I think so, yeah, they'll, they'll be very still, I think they'll be just...
0:14:51 > 0:14:56It's a unique opportunity to film one of the Amazon's most infamous animals.
0:14:56 > 0:15:00You know about all these dangerous creatures and the jau is one of them,
0:15:00 > 0:15:04you know about anacondas, you know about caiman, you know about piranhas,
0:15:04 > 0:15:07but the reality is that none of us have actually seen what they can do,
0:15:07 > 0:15:10you know, we haven't experienced it so...
0:15:10 > 0:15:14In a funny sort of way, you actually feel a little bit, oh,
0:15:15 > 0:15:18it'll be fine, because the reality hasn't hit.
0:15:22 > 0:15:26Kate sets off upstream to check out the information.
0:15:33 > 0:15:35As well as being part of the dive team, over the next month, Kate
0:15:35 > 0:15:39has the added task of tracking down the wildlife on the river margins.
0:15:46 > 0:15:49Oh, this is just extraordinary.
0:15:49 > 0:15:54A family of capybaras on the bank,
0:15:54 > 0:16:02this huge Amazonian rodent. It looks like four young...
0:16:02 > 0:16:08Oh, I just know I'm not gonna want to go back to the boats.
0:16:08 > 0:16:13Think I might run away and stay here.
0:16:13 > 0:16:17But she can't stop for long -
0:16:17 > 0:16:21she needs to find the fishermen that have seen the jau.
0:16:27 > 0:16:31Back downstream, the countdown has started for the dive team.
0:16:31 > 0:16:33- Oxygen supply pressure OK.- Yes.
0:16:33 > 0:16:35Other supply pressure OK.
0:16:35 > 0:16:37- Yes.- Computer electronics turned on.
0:16:37 > 0:16:39Yes.
0:16:39 > 0:16:42- Absorbent time remaining OK.- Yes.
0:16:42 > 0:16:44- Gas flow direction OK.- Fine.
0:16:44 > 0:16:46- Oxygen turned on.- O2 on. - Computer turned on.- Fine.
0:16:46 > 0:16:48- Batteries OK.- Fine.
0:16:58 > 0:17:00The pressure is on.
0:17:00 > 0:17:05They must find and film the creatures concealed by the river's turbid waters.
0:17:14 > 0:17:19Thirty miles upstream, Kate has had a stroke of luck -
0:17:19 > 0:17:22she's found a fisherman who's seen jau.
0:17:23 > 0:17:26Quantos kilos...?
0:17:35 > 0:17:36Mike topside, Mike topside.
0:17:42 > 0:17:44Thank you.
0:17:49 > 0:17:53In the murk, the divers can't find jau.
0:17:53 > 0:17:57In fact, they're struggling to find anything.
0:17:57 > 0:18:03But then, something extraordinary.
0:18:06 > 0:18:13Gradually, in the gloom, a giant colony of sponges appears before their eyes.
0:18:13 > 0:18:18Holy cow, well, I'm just gonna shoot it.
0:18:23 > 0:18:28Normally, these primitive creatures are only ever found in the oceans.
0:18:33 > 0:18:36Looking closer, the divers slowly begin to
0:18:36 > 0:18:40make out camouflaged creatures, motionless amongst the sponges.
0:18:48 > 0:18:54This prehistoric species wears an armour of sharpened scales as a protection from predators.
0:18:56 > 0:19:00Even their fins hide switchblade spines.
0:19:02 > 0:19:08The river reveals an abundance of catfish perfectly adapted to feel
0:19:08 > 0:19:13their way through the darkness with their gigantic whiskers.
0:19:13 > 0:19:17Stay on the catfish, stay on the catfish.
0:19:19 > 0:19:22Oh, he's gone.
0:19:22 > 0:19:26A whole community of exotic fish are hidden here.
0:19:45 > 0:19:49And then almost buried from sight -
0:19:49 > 0:19:52the king of the river bed...
0:19:52 > 0:19:54The giant freshwater stingray,
0:19:54 > 0:19:59its barbed tail laced with enough poison to cripple a diver.
0:20:02 > 0:20:04Extreme stuff.
0:20:04 > 0:20:08A tantalising glimpse before it disappears into the gloom.
0:20:10 > 0:20:15The divers have been in the water for three hours now, and air is running low.
0:20:36 > 0:20:42Suddenly, a little freshwater sponge appears - next to it is a little fish, couldn't get a shot of it,
0:20:42 > 0:20:47thought, "Yeah, that that was interesting, let's keep looking", so we came, kept going up the slope,
0:20:47 > 0:20:52more and more sponges, more and more fish and finally we settled in to a big bed...
0:20:54 > 0:20:58It's the first time this unique habitat has been captured on camera.
0:20:58 > 0:21:02It's weird - what are they doing here?
0:21:02 > 0:21:05You keep reminding yourself that you're in freshwater by tasting it,
0:21:05 > 0:21:10otherwise it looks like you're in the ocean when you see that stuff, they're not supposed
0:21:10 > 0:21:16to be in rivers, everybody knows that. That was pretty spectacular, that was a good fun dive.
0:21:16 > 0:21:19- There is a sense of relief on the dive boat.- Saluje.
0:21:19 > 0:21:21Saluje.
0:21:21 > 0:21:26- Big success.- At last they're starting to find creatures.
0:21:26 > 0:21:31But they all know there are many more spectacular creatures to be discovered.
0:21:35 > 0:21:39First thing next morning, Kate passes on her news.
0:21:39 > 0:21:43I've got a treat for you - I've got reports of jau,
0:21:43 > 0:21:51the big catfish, I met a fisherman up there who caught one - 36 kilos - and he is pretty sure there's another
0:21:51 > 0:21:56one up there because he was descaling a fish in a boat in the middle of the channel and this thing came over.
0:21:58 > 0:22:00And took it.
0:22:00 > 0:22:06Together they start on the journey back up river to the dive site Kate's found.
0:22:06 > 0:22:10Now, look over there, Mike.
0:22:10 > 0:22:15Wow, that's beautiful.
0:22:15 > 0:22:22It may be below that waterfall, lurks our goal...
0:22:22 > 0:22:25Jau.
0:22:25 > 0:22:27Spectacular.
0:22:27 > 0:22:32Comes out of nowhere, almost looks like one of those sort of slightly cheesy backdrops
0:22:32 > 0:22:34you used to get in kind of '70s restaurants.
0:22:34 > 0:22:37I'm just sitting here thinking, we're gonna go diving in that.
0:22:37 > 0:22:39I know!
0:22:46 > 0:22:48My gosh, look at that.
0:22:59 > 0:23:02They are followed by the rest of the dive team,
0:23:02 > 0:23:05and together they set about making camp on the beach.
0:23:23 > 0:23:27The water here is fast flowing and strewn with boulders -
0:23:27 > 0:23:31perfect conditions for jau and many other fish.
0:23:31 > 0:23:34The local delicacy - red-bellied piranha.
0:23:34 > 0:23:37Be underwater.
0:23:37 > 0:23:39Don't need to be underwater.
0:23:39 > 0:23:42Oh, you want to do under, OK.
0:23:42 > 0:23:48The turbulence from the waterfall causes a scum of natural foam.
0:23:51 > 0:23:58The foam blocks out the light and the divers drop into darkness.
0:24:28 > 0:24:35The labyrinth of ledges and caves are a perfect hideout for jau.
0:24:56 > 0:24:57That's better.
0:25:00 > 0:25:05A pike cichlid is captured in the spotlight as it swims for cover.
0:25:37 > 0:25:40In a crevice, catfish shelter
0:25:40 > 0:25:45from hungry predators and keep a watchful eye on passing prey.
0:25:50 > 0:25:55At last, a hint of the incredible life hidden in the river.
0:26:03 > 0:26:10They discover one of the most peculiar creatures of the deep - knifefish.
0:26:11 > 0:26:15These quirks of evolution navigate in the dark waters
0:26:15 > 0:26:21by using a sixth sense - electrical pulses generated by highly adapted muscles.
0:26:21 > 0:26:27They're so specialised they can even talk to each other with their electrical signals.
0:26:38 > 0:26:40And hiding in a sunken log,
0:26:40 > 0:26:44a prize. One of the largest knifefish in the world.
0:26:48 > 0:26:51Called the black ghost, it is shy,
0:26:51 > 0:26:57nocturnal and rare - and has never been filmed in the wild before.
0:26:57 > 0:26:58Holy cow, that's just beautiful!
0:27:06 > 0:27:09There is still no sign of the jau,
0:27:09 > 0:27:14but in this maze of rocks and caverns, its secret lair could be just feet away.
0:27:37 > 0:27:39Fortunately, the piranhas are keeping their distance,
0:27:39 > 0:27:43and now with their air getting low,
0:27:43 > 0:27:46the divers are forced to stop their search for jau.
0:27:56 > 0:27:59We found a lot of fish down there,
0:27:59 > 0:28:03and almost all of them hated the light and were tucked away
0:28:03 > 0:28:05in nasty little rock or wood crevices,
0:28:05 > 0:28:11so you couldn't get a clear shot of them but yeah, we did what we could.
0:28:11 > 0:28:15It's been really nice after my first dive yesterday in that thick soup,
0:28:15 > 0:28:19to come here and see something living in the river, that was good.
0:28:27 > 0:28:32Try as they might, the team could not track down the jau.
0:28:32 > 0:28:39After two days of searching, they are behind schedule, and must move on.
0:28:39 > 0:28:43A decision is made to split into two teams.
0:28:45 > 0:28:49In the first, Mike joins Brazilian professor Mario de Pinna
0:28:49 > 0:28:53on a mission to find creatures never filmed before.
0:28:53 > 0:28:56- Fish that talk. - FISH CROAKS
0:28:56 > 0:29:00Animals that hunt using electricity.
0:29:00 > 0:29:03But their ultimate goal...
0:29:03 > 0:29:07to discover species completely new to science.
0:29:07 > 0:29:11In the second team, Kate Humble heads deep into the jungle.
0:29:11 > 0:29:16Her mission - to track down two of the Amazon's most elusive animals,
0:29:16 > 0:29:19the rare giant otter
0:29:19 > 0:29:24and a strange pink river dolphin - the boto.
0:29:29 > 0:29:33On their quest for new species, Mike and Mario have to cross
0:29:33 > 0:29:36one of the world's great natural spectacles -
0:29:36 > 0:29:38The Meeting of the Waters.
0:29:39 > 0:29:42Here the black waters of the Rio Negro
0:29:42 > 0:29:45join the milky waters of the River Amazon.
0:29:51 > 0:29:56Now how long will this very, very definite line of demarcation last?
0:29:56 > 0:29:58It takes several kilometres,
0:29:58 > 0:30:00- cos the two water types are so different...- Wow.
0:30:00 > 0:30:04..that they actually will not mix for quite some time.
0:30:08 > 0:30:10There we are, getting close.
0:30:10 > 0:30:11Look at that! Astonishing!
0:30:14 > 0:30:20Well, we're now leaving one river...
0:30:20 > 0:30:22entering another.
0:30:24 > 0:30:28Leaving the Rio Negro, they enter the silt-laden Amazon.
0:30:28 > 0:30:30Rich in minerals swept from the Andes,
0:30:30 > 0:30:34this river contains more types of freshwater fish
0:30:34 > 0:30:36than anywhere else on Earth.
0:30:36 > 0:30:39An ideal hunting ground for new species.
0:30:46 > 0:30:49Many people make a living from the river,
0:30:49 > 0:30:53but all are wary of the creatures lurking in these murky waters.
0:30:53 > 0:30:56Mike is searching for one of the most feared of all.
0:30:56 > 0:30:59It's just five centimetres long...
0:30:59 > 0:31:00the candiru.
0:31:00 > 0:31:04The candiru has... a nasty reputation,
0:31:04 > 0:31:08a reputation nastier than pretty much any fish
0:31:08 > 0:31:09I have ever met in my entire life.
0:31:12 > 0:31:14Candiru are vampires,
0:31:14 > 0:31:16parasites of other fish.
0:31:16 > 0:31:19They enter their host's body through the gills
0:31:19 > 0:31:20and gorge on their blood.
0:31:20 > 0:31:23But in the turbid waters of the Amazon,
0:31:23 > 0:31:27they sometimes enter humans by mistake.
0:31:31 > 0:31:34There was the medical record of the guy
0:31:34 > 0:31:38that had the unfortunate experience of a candiru swimming up his penis,
0:31:38 > 0:31:42so now every thing I've been told not to do, we're about to do.
0:31:42 > 0:31:44Go into the water with a little fish
0:31:44 > 0:31:51that has a nasty habit of swimming up your urethra.
0:31:51 > 0:31:55That's right, that's what you're about to do.
0:31:55 > 0:31:59And you will notice very tight mesh.
0:31:59 > 0:32:01The candiru is more common on this beach
0:32:01 > 0:32:03than anywhere else in the Amazon.
0:32:05 > 0:32:08But there's only one way to find them.
0:32:08 > 0:32:10You have to get IN the water.
0:32:13 > 0:32:15I think you will be safe.
0:32:15 > 0:32:19- At least, I hope you will. - All right, that's it.
0:32:19 > 0:32:21I'm committed now.
0:32:21 > 0:32:22BIRDS CAW
0:32:32 > 0:32:36One hundred kilometres away, Kate's team is searching
0:32:36 > 0:32:40for aquatic giants on one of the world's biggest reservoirs.
0:32:40 > 0:32:45When it was dammed in 1987, it drowned half a million trees
0:32:45 > 0:32:47creating a lake larger than Luxembourg.
0:32:49 > 0:32:55It's extraordinary. I mean, it has a kind of ghostly beauty about it.
0:32:58 > 0:33:02This area now, partly because it's so protected,
0:33:02 > 0:33:07has become home not just to a huge diverse population of fish,
0:33:07 > 0:33:13including the black piranha, which is the most fearsome of them all,
0:33:13 > 0:33:17but also to turtles and to giant otters.
0:33:17 > 0:33:19Very, very exciting.
0:33:31 > 0:33:35But finding the otters in this vast area won't be easy -
0:33:35 > 0:33:39less than 5,000 remain in the whole of South America.
0:33:40 > 0:33:44After six hours of looking, Kate hasn't seen a trace of an otter.
0:33:44 > 0:33:49But this remote reservoir has become home to a huge variety of wildlife.
0:33:52 > 0:33:54It's incredible.
0:33:57 > 0:33:59There is so much to look at.
0:34:03 > 0:34:07Mike's team are having no more luck in their search for the candiru,
0:34:07 > 0:34:10but they have netted a trawl of bizarre little aliens
0:34:10 > 0:34:15whose ancestors originally came from the ocean 1,000 miles away.
0:34:16 > 0:34:18Look at those teeth.
0:34:18 > 0:34:21It's a needle fish.
0:34:21 > 0:34:25I have a marine version of this that looks exactly like this actually.
0:34:25 > 0:34:28Snappy little fella too. All right, all right.
0:34:29 > 0:34:32This is everybody's favourite,
0:34:32 > 0:34:36it's a puffer fish. When a predator takes him,
0:34:36 > 0:34:40he puffs up and they can't get him down, so they let him go
0:34:40 > 0:34:43or he can go into a crack and puff up
0:34:43 > 0:34:44and he can't be extracted.
0:34:44 > 0:34:48I need to get him back in the water pretty quickly though.
0:34:48 > 0:34:54No sign of candiru yet, but instead a fish that wards off predators...
0:34:54 > 0:34:55Check this guy out.
0:34:55 > 0:34:58- ..by talking.- This is a doradid
0:34:58 > 0:34:59Doradid.
0:34:59 > 0:35:03- Armoured catfish. - FISH CROAKS
0:35:05 > 0:35:09It's a...makes these sounds trying to get rid of you.
0:35:09 > 0:35:13Go ahead, bring it up. Here we go. Come on, say hi.
0:35:13 > 0:35:16FISH CROAKS
0:35:16 > 0:35:18- Be careful of... - He's saying, "Please let me go."
0:35:18 > 0:35:21All right, I'm letting this guy go.
0:35:21 > 0:35:27See, ya. Well done, obrigado.
0:35:30 > 0:35:34Kate's found another distraction on her search for giant otters.
0:35:34 > 0:35:38A skimmer - plucking fish from the surface of the water.
0:35:39 > 0:35:43BOTO HOOTS Ooh! Oh, my God!
0:35:46 > 0:35:52I want to get in the water, we're absolutely surrounded by botos.
0:35:52 > 0:35:55Boto, a pink freshwater dolphin...
0:35:55 > 0:35:59Well, this six hour journey has now extended
0:35:59 > 0:36:04to...I think about eight hours.
0:36:05 > 0:36:07It's entirely my fault.
0:36:07 > 0:36:09There's so much to look at.
0:36:12 > 0:36:15- CREWMAN:- We have to make camp before...
0:36:15 > 0:36:17We have to make camp before it gets dark.
0:36:17 > 0:36:20I must stop, we're here for two days. I'm sorry.
0:36:20 > 0:36:23Desculpe. Vamos!
0:36:27 > 0:36:29Right on the bottom...
0:36:29 > 0:36:32Mike and his team have been in the water two hours.
0:36:37 > 0:36:39If a candiru enters their body
0:36:39 > 0:36:42they'd need emergency surgery to cut it out.
0:36:46 > 0:36:47OK. There's one.
0:36:47 > 0:36:53But at last he catches one, fortunately in the net.
0:36:53 > 0:36:57These fish have modified teeth outside of their mouth,
0:36:57 > 0:37:01so these are not real spines, they're actually teeth.
0:37:01 > 0:37:03That's what all the fuss is about...
0:37:03 > 0:37:07candiru, candiru - the famous or infamous.
0:37:07 > 0:37:09Now when they're full of blood,
0:37:09 > 0:37:12presumably this will be a little larger in diameter and red.
0:37:12 > 0:37:16- Yeah, yeah, they go to about twice this size.- Oh, I can feel those.
0:37:16 > 0:37:20- Oh, you can feel the teeth, yeah? - Spines...the teeth, yes.
0:37:20 > 0:37:22So now you can see how it actually moves
0:37:22 > 0:37:25when it's trying to get into something.
0:37:27 > 0:37:31Buoyed up by their success, they move on to their ultimate goal -
0:37:31 > 0:37:34to discover species completely new to science.
0:37:42 > 0:37:44- They go in here, Ian.- >
0:37:44 > 0:37:47The team are going to try a new tactic -
0:37:47 > 0:37:48to dive in the dead of night.
0:37:48 > 0:37:52They use the daylight for preparing their gear.
0:37:55 > 0:38:00Underwater cameramen Mike Pitts makes his final equipment check.
0:38:00 > 0:38:05Nine-tenths of any job underwater is done up here.
0:38:05 > 0:38:09Simple - it? Well the simpler you make it up here,
0:38:09 > 0:38:13it's so much easier when you're down there, but the camera system is ready to go.
0:38:20 > 0:38:22It's time to test their theory.
0:38:22 > 0:38:25- Absorbent time remaining, OK?- Yeah.
0:38:25 > 0:38:28OK. Computer electronics turned on?
0:38:28 > 0:38:30- Yeah.- Diluent analysed?
0:38:30 > 0:38:32Oxygen turned on?
0:38:32 > 0:38:35Yeah.
0:38:35 > 0:38:37Diving at night is more dangerous.
0:38:37 > 0:38:40It's all too easy to get lost in the darkness.
0:38:40 > 0:38:47If anything goes wrong, they're totally on their own, the nearest hospital is three days away.
0:38:47 > 0:38:49God, they're all in.
0:38:49 > 0:38:53Leaks...weights... all sorts of things,
0:38:53 > 0:38:56currents in different directions, but they're all in.
0:38:56 > 0:38:59I'm getting happier by the minute and they're all going for it.
0:38:59 > 0:39:01OK. Let's go.
0:39:11 > 0:39:14This alien world may seem empty.
0:39:14 > 0:39:18but in these depths, strange creatures do exist.
0:39:30 > 0:39:33The blind tube-snout -
0:39:33 > 0:39:36one metre long, but only a centimetre thick.
0:39:36 > 0:39:43It uses pulses of electricity to communicate and find food in the gloom.
0:39:45 > 0:39:47But when the fish come out...
0:39:47 > 0:39:48so do the predators.
0:39:48 > 0:39:50ECHOING CALL
0:39:50 > 0:39:57Somewhere in the darkness, a boto dolphin is searching for prey with sonar.
0:40:09 > 0:40:12Suddenly, there's a problem.
0:40:12 > 0:40:15Mike Pitts' air supply has malfunctioned.
0:40:17 > 0:40:20He's 20 metres below the surface
0:40:20 > 0:40:23and in danger of losing consciousness.
0:40:35 > 0:40:36- DIVER:- Certainly will.
0:40:39 > 0:40:43Despite the urgency, it's crucial they ascend slowly.
0:40:43 > 0:40:47Coming up too fast can cause serious medical injuries,
0:40:47 > 0:40:48including the bends.
0:40:53 > 0:40:55Port stern!
0:40:55 > 0:40:59Stand by, while I do a pan of the light.
0:40:59 > 0:41:03We'll tell them we're on the bow and I'm going over to the top lines.
0:41:03 > 0:41:09- DIVER:- We'll be extra vigilant when we come up.
0:41:09 > 0:41:13Both of their computers are yelping like crazy.
0:41:13 > 0:41:17Pitts is out of the water still with a re-breather problem.
0:41:17 > 0:41:23- Jesus.- The guys are just over an hour into their dive and they had a re-breather problem.
0:41:23 > 0:41:25I'm not entirely sure what it was,
0:41:25 > 0:41:27it sounds like some electronics had gone down
0:41:27 > 0:41:30and they'll have to fly them manually.
0:41:30 > 0:41:33We've taken first aid precautions.
0:41:33 > 0:41:36The last little bit of their ascent
0:41:36 > 0:41:37was quite rapid, right?
0:41:37 > 0:41:40And it's that last little bit that is important.
0:41:40 > 0:41:45We've put them on pure oxygen as a precaution.
0:41:45 > 0:41:48I half considered dropping the camera -
0:41:48 > 0:41:50- half considered it. - Oh, that's pretty serious.
0:41:50 > 0:41:54Then I thought I can't control it properly with the camera,
0:41:54 > 0:41:55so I better just drop it.
0:41:55 > 0:41:58You feeling all right, fellas? Just give me a thumbs up.
0:42:03 > 0:42:06The incident drives home just how alone they really are.
0:42:16 > 0:42:20Next morning, Kate's been joined by Fernando Rosas
0:42:20 > 0:42:24who has spent four years studying giant otters.
0:42:24 > 0:42:26He knows that to have any chance of filming them,
0:42:26 > 0:42:29they must start their search at dawn.
0:42:31 > 0:42:32It's just gone five in the morning,
0:42:32 > 0:42:35so we're feeling a little bit bleary eyed
0:42:35 > 0:42:38and Fernando and I are on a quest
0:42:38 > 0:42:43to see if the giant otters are having more of a lie-in than us.
0:42:45 > 0:42:49Fernando often goes days without seeing an otter
0:42:49 > 0:42:51and he's developed some unconventional techniques
0:42:51 > 0:42:53to find them.
0:42:53 > 0:42:56Yeh, yeh, yeh, yeh, yeh, yeh, yeh!
0:42:56 > 0:42:59Yeh, yeh, yeh, yeh! Phroo, phroo...
0:43:01 > 0:43:04That's obviously good morning in otter language.
0:43:07 > 0:43:10And this is the den, you see, underneath the vegetation.
0:43:10 > 0:43:13- Under, yes.- The entrance of the den here and there.
0:43:13 > 0:43:15I'm also collecting some faeces
0:43:15 > 0:43:18to know what they are eating here in the lake,
0:43:18 > 0:43:23because we know giant otters, they eat mainly fish like piranhas.
0:43:23 > 0:43:25And what sort of piranhas are in this lake?
0:43:25 > 0:43:27Mainly black piranhas - the big ones.
0:43:27 > 0:43:32Yeah, they can reach up to two kilos, they are big, big animals.
0:43:32 > 0:43:35- And very aggressive. - They are very aggressive.
0:43:35 > 0:43:38This lake is teeming with black piranhas.
0:43:38 > 0:43:40It should be perfect otter territory.
0:43:53 > 0:43:56Mike and Mario are still on the search for new species.
0:43:56 > 0:44:00It's going to take them to places far too shallow for the main boat.
0:44:07 > 0:44:10The Amazon's small streams are crystal clear
0:44:10 > 0:44:12because it hasn't rained for weeks.
0:44:12 > 0:44:15This might be their best chance to find new life.
0:44:20 > 0:44:22Drag your fingers through the sand.
0:44:22 > 0:44:25But nothing's that simple in the Amazon.
0:44:25 > 0:44:27THUNDER CRASHES
0:44:30 > 0:44:32It makes me wonder how stupid we are
0:44:32 > 0:44:37standing in water while that kind of activity is going on.
0:44:40 > 0:44:45This rain is going to wash down this exposed clay and mud
0:44:45 > 0:44:47and it's going to turn to muck.
0:44:47 > 0:44:50It seems their best hope of finding animals new to science
0:44:50 > 0:44:52is being washed away in the mud.
0:44:52 > 0:44:55Finally, we find a place where we think we can work
0:44:55 > 0:45:00and this is what happens. That's typical, isn't it?
0:45:00 > 0:45:03My God, look at what's happening the other side.
0:45:10 > 0:45:15Back at the reservoir, the sun is shining on Kate and Fernando,
0:45:15 > 0:45:19but that means the otters may have left their dens for the day.
0:45:22 > 0:45:26The opportunity to film them may already have been lost.
0:45:35 > 0:45:37They are there. They are leaving the den.
0:45:37 > 0:45:39Yes, look! Look - up on the bank.
0:45:39 > 0:45:40- Up on the bank.- That's right.
0:45:40 > 0:45:43Was that call a warning call
0:45:43 > 0:45:46- or is it a sort of...? - Just kind of alert...
0:45:46 > 0:45:51They are relaxed, they are not alarmed, they are not in danger, they know us.
0:45:51 > 0:45:55It's just like a little constant chuntering going on. Chick, chick, chick.
0:45:56 > 0:45:58This one's got a fish there -
0:45:58 > 0:46:01a big fish.
0:46:01 > 0:46:03Just getting a better grip.
0:46:07 > 0:46:09They cover so much ground so quickly
0:46:09 > 0:46:12- And they swim very fast.- Very fast.
0:46:12 > 0:46:18Hunted for years for their fur, they were nearly driven to extinction.
0:46:18 > 0:46:22Here, at least, they are safe.
0:46:24 > 0:46:30- From the front, when you can't see the tail, they look amazingly like sea lions.- Yeah.
0:46:30 > 0:46:33Tiny little ears...
0:46:33 > 0:46:36Because the feet are totally webbed they could almost be flippers.
0:46:36 > 0:46:40- (So they can swim, yeah?)- (Yeah.)
0:46:40 > 0:46:43So do you think this might be the alpha male and female?
0:46:43 > 0:46:45- Those two here?- I guess so.
0:46:45 > 0:46:49I can see why you come back...
0:46:49 > 0:46:54..year after year after year. They're just...magnificent.
0:46:56 > 0:46:59I just don't see this working.
0:46:59 > 0:47:01Mike's having no luck at all.
0:47:01 > 0:47:05The rain has spoilt his chances of filming anything.
0:47:06 > 0:47:08- No, this is going to be muddy - for the rest of the day.
0:47:08 > 0:47:11Hey, Mario!
0:47:11 > 0:47:17This just isn't gonna work. I can't see anything. I think we catch them, put them in the aquarium.
0:47:17 > 0:47:19Please!
0:47:19 > 0:47:23Filming animals in ankle-deep mud is impossible.
0:47:23 > 0:47:25Mike and biologist Mario
0:47:25 > 0:47:29decide to catch and film fish in a tank instead.
0:47:30 > 0:47:34Oh! Oh! Look at that.
0:47:34 > 0:47:38Here we have several representatives of the...
0:47:38 > 0:47:40- This is a...- That's a catfish...
0:47:40 > 0:47:42I can't believe this, just one...
0:47:42 > 0:47:46- One.- Is this common here - just one scoop and you get a dozen fish?
0:47:46 > 0:47:48Yeah, yeah. There's a lot of life,
0:47:48 > 0:47:52it's amazing how little water can hold so much life, it's fantastic.
0:47:52 > 0:47:57- Amazing.- In the net, Mario spots something that looks different.
0:47:57 > 0:48:01If we can put them temporarily in a tank then if we...
0:48:01 > 0:48:04Yes, well we have been...
0:48:04 > 0:48:06These people live beside a small stream
0:48:06 > 0:48:11that has as many types of fish as all the rivers in Britain combined.
0:48:13 > 0:48:20The team set up a portable jungle studio to film the unusual fish.
0:48:20 > 0:48:24Tiny fish is where the great things to be discovered are.
0:48:24 > 0:48:26That's lovely.
0:48:28 > 0:48:31- PITTS: It's really small. - Right in front of the tripod.
0:48:31 > 0:48:35It looks like just a tiny little white one. That's what we need.
0:48:35 > 0:48:37OK. Well!
0:48:41 > 0:48:46At last, they've found what they've been looking for...a new species.
0:48:48 > 0:48:51This is perfect, this is ichthyological history.
0:48:51 > 0:48:54Just fantastic.
0:48:54 > 0:48:56Hold that there.
0:48:56 > 0:48:59That's a great view of its stomach.
0:48:59 > 0:49:02- Boy, that is no doubt that that's blood.- Yes.
0:49:02 > 0:49:06This is a new species of something really weird that sucks blood.
0:49:06 > 0:49:09In addition to all of that, it has become really small,
0:49:09 > 0:49:12so it can actually use the fish in these little creeks.
0:49:12 > 0:49:16It's a new species of blood-sucking catfish.
0:49:16 > 0:49:21It may be small, but it's an important scientific discovery.
0:49:21 > 0:49:24No doubt this is blood...
0:49:24 > 0:49:26Animal vampires often possess chemicals
0:49:26 > 0:49:29that thin the blood of their victims.
0:49:29 > 0:49:30It's possible their discovery
0:49:30 > 0:49:33could lead to better treatments for heart disease.
0:49:33 > 0:49:37- Well done, Mario!- Yeah. - Bungling amateurs.
0:49:41 > 0:49:43After Kate's success with the otters,
0:49:43 > 0:49:47she's determined to find the boto dolphins.
0:49:47 > 0:49:49She's had a tip-off.
0:49:49 > 0:49:54It seems the best place to find wild boto is the local beach resort.
0:50:11 > 0:50:15This small town has become quite famous for this little restaurant,
0:50:15 > 0:50:16which is just over here,
0:50:16 > 0:50:19because the daughters of the owners of this restaurant
0:50:19 > 0:50:25have been feeding the dolphins and it may be that not only can I feed them,
0:50:25 > 0:50:27but I can get into the water with them.
0:50:36 > 0:50:38Kate lures the boto in,
0:50:38 > 0:50:42so that the sound recordist can try to make a rare underwater recording
0:50:42 > 0:50:43of their calls.
0:50:43 > 0:50:46BOTOS CLICK
0:50:48 > 0:50:52RECORDING PLAYS BOTOS CLICKING
0:50:53 > 0:50:55Even though they're coming right up here...
0:50:57 > 0:51:00..you still, can't really get an idea of what they look like
0:51:00 > 0:51:02because it's so dark down there.
0:51:02 > 0:51:04I want to see your face.
0:51:04 > 0:51:06SHE LAUGHS
0:51:07 > 0:51:09There's one right here.
0:51:11 > 0:51:13Unbelievable.
0:51:14 > 0:51:19Extraordinary beaks - they've got long rows of teeth on either side.
0:51:19 > 0:51:22Totally twisted beak...
0:51:24 > 0:51:26Oh, there's a big one here.
0:51:26 > 0:51:32Got these really big, kind of, bulging foreheads,
0:51:32 > 0:51:34which is the sonar.
0:51:34 > 0:51:38Which they definitely need in water this dark.
0:51:40 > 0:51:43A constant clicking, clicking.
0:51:43 > 0:51:45Is there any...? Have you noticed like
0:51:45 > 0:51:48when they come up and take fish does the sound change or...?
0:51:48 > 0:51:51It's like, when they're coming in they start...
0:51:57 > 0:52:00Now that Kate's attracted the botos,
0:52:00 > 0:52:03the camera team can get in the water.
0:52:03 > 0:52:06But they've no idea how these dolphins will react.
0:52:09 > 0:52:10Woh!
0:52:22 > 0:52:24The dolphins show no fear of the cameraman
0:52:24 > 0:52:27as they swim through their strange world,
0:52:27 > 0:52:30stained deep red from the rainforest's leaves.
0:52:38 > 0:52:40They like your bit better.
0:52:41 > 0:52:42This is fantastic!
0:52:49 > 0:52:52Kate's team are achieving their goal
0:52:52 > 0:52:57by capturing remarkable underwater images of these amazing animals.
0:52:57 > 0:53:02They're also discovering that wild botos can be surprisingly gentle.
0:53:04 > 0:53:06There's this, um...
0:53:06 > 0:53:08There are various stories,
0:53:08 > 0:53:11legends about boto - that they take human form
0:53:11 > 0:53:15and whisk away the prettiest girls in the village
0:53:15 > 0:53:19and it's very strange, looking at them underwater
0:53:19 > 0:53:20they do look curiously human
0:53:20 > 0:53:23because their skin is the same colour as ours
0:53:23 > 0:53:30and, you know, they have this sort of quite human looking form underwater.
0:53:34 > 0:53:37BOTOS CLICK
0:53:48 > 0:53:51Well, I think...
0:53:51 > 0:53:54they are officially full.
0:53:54 > 0:53:56There's one down here tickling my feet.
0:53:56 > 0:53:58Oh, there you are! Do you want it?
0:53:58 > 0:54:01That's it, no more fish.
0:54:01 > 0:54:04What an amazing...
0:54:04 > 0:54:05amazing experience.
0:54:11 > 0:54:16Kate heads back to the ships, and together they travel upstream
0:54:16 > 0:54:20to their next destination.
0:54:20 > 0:54:24With all the experience they've gained, their next challenge
0:54:24 > 0:54:29is to dive the very deepest part of the Amazon.
0:54:29 > 0:54:34Hidden in the water is an abyss - a 90m-deep channel
0:54:34 > 0:54:41gauged into the river bed. Scientists have no idea what lies in its depths.
0:54:49 > 0:54:53I feel very comfortable we will see something we have not seen before.
0:54:53 > 0:54:58I really strongly feel that. We will be far deeper than we've been before,
0:54:58 > 0:55:01and I'm really excited about what we're doing right now.
0:55:01 > 0:55:06The expedition is about to start its second phase.
0:55:16 > 0:55:21The team plan to take cameras into this abyss to find and film
0:55:21 > 0:55:23the creatures that hide there.
0:55:42 > 0:55:47The three Amazon riverboats head off once more along the mightiest river in the world.
0:55:47 > 0:55:51The abyss they are seeking is 1,000 miles from the sea
0:55:51 > 0:55:54and they will have to journey through the night to reach it.
0:56:00 > 0:56:02But nothing goes to plan in the Amazon.
0:56:02 > 0:56:05CRASH!
0:56:05 > 0:56:10They've struck bottom. The boat has juddered to a halt.
0:56:10 > 0:56:14The shaft is bent? Struts, flapping?
0:56:14 > 0:56:20The problem is the strut is bolted into the hull. You knock it to the side, it pulls a piece of wood,
0:56:20 > 0:56:22a hole in the hull!
0:56:22 > 0:56:26Mike Pitts volunteers to inspect the damage.
0:56:26 > 0:56:32We've taken on water through this. If that starts with a vengeance,
0:56:32 > 0:56:34voom! Down it'll go.
0:56:34 > 0:56:39The momentum of a 60-ton vessel going over a rock,
0:56:39 > 0:56:42- it will open it up like a can of sardines.- Not good.
0:56:48 > 0:56:52The boat is taking on water and the propeller is bent.
0:56:52 > 0:56:59In the darkness, two divers grope their way on the bottom of the hull,
0:56:59 > 0:57:03hoping to find the full extent of the damage.
0:57:03 > 0:57:07- 'It's surface.'- Pretty gloomy!
0:57:09 > 0:57:13They're marooned on a sandbank in the middle of the Amazon.
0:57:15 > 0:57:19The expedition has juddered to a halt.