0:00:04 > 0:00:09Crocodiles have roamed the earth for over 100 million years.
0:00:12 > 0:00:15Yet much of their lives remain a mystery.
0:00:17 > 0:00:19Look at the size of that crocodile there!
0:00:21 > 0:00:25These giant reptiles kill hundreds of people in Africa every year.
0:00:26 > 0:00:30That was really quick. That was like a gun!
0:00:31 > 0:00:35To help reduce attacks, we need to understand their behaviour.
0:00:35 > 0:00:3830 centimetres below him, watching him, and it just snapped...
0:00:38 > 0:00:40- Snapped on the camera. - It was ridiculous.
0:00:40 > 0:00:44So I'm in Botswana, joining a research team who,
0:00:44 > 0:00:49for the first time ever, will attempt to study them underwater.
0:00:49 > 0:00:51Three, two, one.
0:00:53 > 0:00:58If successful, the expedition could revolutionise our understanding
0:00:58 > 0:01:00of these majestic creatures.
0:01:01 > 0:01:03Holy crap.
0:01:03 > 0:01:06This has got to be one of the most extraordinary encounters
0:01:06 > 0:01:09I've ever had.
0:01:09 > 0:01:12But it's a challenge fraught with risk.
0:01:12 > 0:01:13They attacked you?
0:01:13 > 0:01:16Right from behind. Came right behind us.
0:01:16 > 0:01:18I had to use the camera, it got the bloody light in its mouth.
0:01:18 > 0:01:21That's kind of totally thrown me.
0:01:29 > 0:01:33I've come to Botswana's Okavango Delta in southern Africa.
0:01:33 > 0:01:37It's a massive wetland the size of Switzerland
0:01:37 > 0:01:40and home to Africa's Nile crocodile.
0:01:54 > 0:01:59Like most people, I know very little about crocodiles.
0:01:59 > 0:02:03But I'm about to get a unique insight into their behaviour.
0:02:03 > 0:02:07- I'm Ben, very nice to see you. How are you?- Pleased to meet you. - Thank you very much.
0:02:07 > 0:02:09- Need a hand?- That would be great.
0:02:09 > 0:02:13'For the next ten days, I'll be working on a groundbreaking project
0:02:13 > 0:02:18'with a team pioneering the study of wild crocodiles underwater.'
0:02:18 > 0:02:22It still, to me, seems slightly ridiculous
0:02:22 > 0:02:25that I'm actually going in the water with crocodiles.
0:02:25 > 0:02:32But, you know, right now, I've still got my getting-in-the-water hat on.
0:02:33 > 0:02:36'The core diving team will be based here at Nxamaseri Lodge.'
0:02:36 > 0:02:39- Hey.- Hey.
0:02:39 > 0:02:43'In the heart of one of Africa's richest areas of natural wildlife.'
0:02:43 > 0:02:46Nice spot for a lodge. Could it be any remoter?
0:02:47 > 0:02:51- Nice to meet you.- Nice to meet you. Andy.- How are you?- Good, thanks.
0:02:51 > 0:02:53It's beautiful. How long have you been here?
0:02:53 > 0:02:56'Once I've dropped off my bags and before we begin our study proper,'
0:02:56 > 0:02:59I head out onto the water with one of our team
0:02:59 > 0:03:02for my first encounter with a Nile crocodile.
0:03:03 > 0:03:05We have crocodiles all around us,
0:03:05 > 0:03:09but the ones we're going to see are going to be the adults, most likely.
0:03:09 > 0:03:11And we get quite a few adults in this section of the river.
0:03:11 > 0:03:15If we're lucky we'll see a nice big, four-metre.
0:03:15 > 0:03:16'Ecologist Vince Shacks
0:03:16 > 0:03:20'has been monitoring the local crocodile population for the last seven years.'
0:03:20 > 0:03:23- There we go, there we go. - Is it this one here?
0:03:23 > 0:03:25Yeah.
0:03:25 > 0:03:28Wow. That's a big croc!
0:03:28 > 0:03:30So what sort of size do you think that is?
0:03:30 > 0:03:34It's around three metres. Yeah. Maybe even three-and-a-half.
0:03:34 > 0:03:37'Nile crocodiles can grow up to six metres and weigh as much as a car.
0:03:37 > 0:03:40'Some live to be 100 years old.'
0:03:40 > 0:03:44- Look at those teeth!- Adults normally start losing their teeth
0:03:44 > 0:03:47and losing a lot of condition in their teeth at this sort of age,
0:03:47 > 0:03:48so it's in pretty good shape.
0:03:48 > 0:03:52Got a nice, big, fat neck. Big, bulky head.
0:03:52 > 0:03:55When the adults get old, they start getting really gnarly features.
0:03:55 > 0:03:58All the bones start popping out.
0:03:58 > 0:04:03- Already, this is the closest I've ever been to a crocodile.- OK.
0:04:03 > 0:04:06They are extraordinary looking things, aren't they?
0:04:06 > 0:04:10And ooh, look, look, look, here it goes!
0:04:10 > 0:04:11That's quick!
0:04:11 > 0:04:14Wow, that's a bit disconcerting! Is it under us, then?
0:04:14 > 0:04:19- It'll be straight underneath us, yeah.- We can't see it.- Yeah, it's pretty murky there.- Gone.
0:04:19 > 0:04:22It'll come down and sneak into the shadows over here and sit still.
0:04:22 > 0:04:24- Yeah.- Very calmly wait for us to leave.
0:04:24 > 0:04:28- And then take up its position again? - Get back up again, yeah.- Wow!
0:04:30 > 0:04:33Oh, look at that!
0:04:33 > 0:04:37These crocodiles spend around 80% of their lives submerged.
0:04:37 > 0:04:39Woah!
0:04:41 > 0:04:47'Until the 1970s, crocodiles here were hunted for their skins.'
0:04:47 > 0:04:50- They really blend in. - They really do that, they really do.
0:04:50 > 0:04:53There in the water, that's it, it's gone.
0:04:53 > 0:04:55'But since the practice was outlawed,
0:04:55 > 0:05:00'numbers have rallied in the Delta Panhandle to over 3,000.'
0:05:00 > 0:05:04Can you tell, by looking at a crocodile from that distance,
0:05:04 > 0:05:06maybe, do you recognise indiv...
0:05:06 > 0:05:08- If you recognise it. - I thought that was a crocodile!
0:05:08 > 0:05:11- That's how jumpy I am! - Let's just get out of here.
0:05:11 > 0:05:14It does, it makes you jumpy, we're out here...
0:05:14 > 0:05:15It does, like, everywhere.
0:05:22 > 0:05:28'Vince's job is to monitor the health of the crocodile population.
0:05:28 > 0:05:32'And his research methods couldn't be more hands on.'
0:05:33 > 0:05:37Woah, you caught it! Oh, my God!
0:05:37 > 0:05:39You're like Crocodile Dundee!
0:05:39 > 0:05:44This is just small, so obviously the size we're looking for is a lot bigger than this.
0:05:44 > 0:05:47But it's probably a good time to just let you grasp the animal
0:05:47 > 0:05:50- and get used to it.- Grasp the animal? Yeah, OK.- Yeah, you can have...
0:05:50 > 0:05:54- What size is this?- Oh, this is probably about 80 centimetres.
0:05:54 > 0:05:57See, so if I let the jaws relax and they just open,
0:05:57 > 0:05:59kind of getting ready to bite anything.
0:05:59 > 0:06:03- If you want to just grab...- Yeah. - Grab the jaws first. The head there.
0:06:03 > 0:06:08- You'll feel the top of the...- Yeah, it's powerful.- Just like that.- Wow! - You've got those jaws?- Just about.
0:06:08 > 0:06:12'Full grown crocodiles have the strongest bite of any reptile
0:06:12 > 0:06:15'on Earth. More powerful than a T-rex.
0:06:15 > 0:06:18'But you can hold their jaws shut surprisingly easily.'
0:06:18 > 0:06:20I'm holding a crocodile.
0:06:20 > 0:06:22OK, I admit it's quite small.
0:06:22 > 0:06:25- Look, its jaw's opening, is that OK? - As soon as you ease the pressure...
0:06:25 > 0:06:29- Oh, yeah!- You see you can close it very easily.- Hello.- Yeah.
0:06:29 > 0:06:33What he's trying to do is he's trying to open and get ready for a bite.
0:06:33 > 0:06:36These are the scutes that we use to mark the animal with, so these
0:06:36 > 0:06:40are the ones that we'll cut off of the larger animals to identify them.
0:06:40 > 0:06:43They act as a fingerprint because the patterns here are unique
0:06:43 > 0:06:45to every crocodile.
0:06:48 > 0:06:50You did that with your hands!
0:06:51 > 0:06:54Wow! That's a bit bigger!
0:06:54 > 0:06:56It's a bit bigger. Right, then.
0:06:56 > 0:07:00OK, here's some tape, yeah, here we go.
0:07:00 > 0:07:02That is a big... You got him?
0:07:02 > 0:07:03Yeah.
0:07:03 > 0:07:05What sort of size do you think this is?
0:07:05 > 0:07:11It's probably a 1.2, 1.2 metres?
0:07:11 > 0:07:14- That's all you're going to do his mouth with?- Yeah.
0:07:14 > 0:07:18- A piece of Sellotape. - The tail scutes are still intact,
0:07:18 > 0:07:21so this animal's never been caught before.
0:07:21 > 0:07:25So yeah, he is a new guy.
0:07:25 > 0:07:27And what sort of age do you think this one is?
0:07:27 > 0:07:31- Wow! It's an amazing noise they make.- It is, yeah.
0:07:31 > 0:07:33Very low pitched growl.
0:07:33 > 0:07:35CROCODILE GROWLS
0:07:36 > 0:07:40He's basically just filling his lungs up to prepare to do something.
0:07:41 > 0:07:43As we head for home,
0:07:43 > 0:07:46I catch a glimpse of a huge crocodile under our boat.
0:07:46 > 0:07:49- It's moving, it's moving, it's moving!- Yeah.
0:07:53 > 0:07:56See his head there?
0:07:56 > 0:07:58Oh, my God, look at the size of that!
0:08:01 > 0:08:04I have actually got goosebumps all up and down my arms.
0:08:04 > 0:08:06- It's unbelievable.- Unbelievable.
0:08:06 > 0:08:09- I've never seen a crocodile like that underwater.- Yeah.
0:08:09 > 0:08:14'It's sobering to think we'll be diving with crocodiles this size
0:08:14 > 0:08:16'and much bigger.
0:08:25 > 0:08:29'Back at Nxamasari Lodge, I meet up with the team that I'll dive with
0:08:29 > 0:08:30'for the next ten days -
0:08:30 > 0:08:34'husband and wife, Brad Bestelink and Andy Crawford.
0:08:34 > 0:08:38'Both expert divers and wildlife photographers.
0:08:38 > 0:08:43'Leading this pilot research will be British zoologist Dr Adam Britton.
0:08:43 > 0:08:46'This will be Adam's first chance
0:08:46 > 0:08:48'to study wild crocodiles underwater.'
0:08:49 > 0:08:51This is like a marriage made in heaven.
0:08:51 > 0:08:55You've got the two first crocodile divers,
0:08:55 > 0:08:58and Adam, you're pretty much the world expert on crocodiles.
0:08:58 > 0:09:03I have wanted to do what you guys are doing for years,
0:09:03 > 0:09:07because I thought to myself, "Look, these crocodiles,
0:09:07 > 0:09:10"people misinterpret them, they misunderstand them.
0:09:10 > 0:09:13"They're not the animals people think they are."
0:09:13 > 0:09:15We're familiar with what they do underwater,
0:09:15 > 0:09:18but we don't know the science behind why, you know,
0:09:18 > 0:09:21and it opened our eyes to how we can work with them underwater.
0:09:21 > 0:09:25I'm very nervous about this. I mean, I will... Yeah.
0:09:25 > 0:09:28- I have genuine nerves now.- Yeah.
0:09:28 > 0:09:31But you should be apprehensive. It's completely normal.
0:09:31 > 0:09:34I mean, I am a little bit apprehensive, to be honest.
0:09:34 > 0:09:37I'm also incredibly excited and that tends to override it
0:09:37 > 0:09:40but, at the same time, there's always that little inkling of fear
0:09:40 > 0:09:43in the back of your mind thinking, "What if they're wrong?"
0:09:43 > 0:09:46or, "What if this is the one time when it doesn't go to plan?"
0:09:46 > 0:09:49That's why we're so strict on the safety
0:09:49 > 0:09:54and, just, we're relying very much on crocs being what they are.
0:09:54 > 0:09:58As long as we can minimise ourselves posing as a prey species,
0:09:58 > 0:10:02that's going to increase our chances of having great interactions.
0:10:02 > 0:10:05So presumably, the first thing is to get us in the water?
0:10:05 > 0:10:08Yeah. You've got to get in the water, that's right, today.
0:10:08 > 0:10:10- Today?- Today. This afternoon.
0:10:16 > 0:10:19- In here, Brad, this one?- Yep.
0:10:19 > 0:10:21Don't forget the sunblock and the hat.
0:10:21 > 0:10:23Before we go anywhere near a crocodile,
0:10:23 > 0:10:27I need to get used to the unique diving conditions
0:10:27 > 0:10:29in the Okavango Delta.
0:10:33 > 0:10:36We head out along the main channel to look for a spot
0:10:36 > 0:10:39that's crocodile-free.
0:10:44 > 0:10:46Hold on, guys! Hold on, there's an elephant!
0:10:46 > 0:10:49- There's an elephant in the reeds, there.- Elephant!
0:10:50 > 0:10:52There's two.
0:10:57 > 0:11:02I mean, if there's anything that reminds you we're in the middle of Africa now...
0:11:02 > 0:11:05You get desensitised. Here we are on a river,
0:11:05 > 0:11:09and suddenly you come across two elephants. Wow.
0:11:09 > 0:11:13Brad and Andy became croc divers by accident.
0:11:13 > 0:11:16They came across one unexpectedly while making a wildlife film
0:11:16 > 0:11:21in these waters and were astonished when it didn't attack.
0:11:21 > 0:11:23- Yeah, big one.- Wow, it's a big one!
0:11:24 > 0:11:27Since then, they've developed a system
0:11:27 > 0:11:32to dive with Nile crocodiles and have got to know many of them well.
0:11:32 > 0:11:36Javier's an old male that we started seeing about two years ago.
0:11:38 > 0:11:42I love the fact that you give wild creatures names like Javier,
0:11:42 > 0:11:44for a crocodile.
0:11:44 > 0:11:47- He is a beautiful crocodile.- OK.
0:11:47 > 0:11:49So my wife named him. OK, after who?
0:11:49 > 0:11:51After the actor. Javier Bardem.
0:11:51 > 0:11:54Oh, OK. I'm with you!
0:11:54 > 0:11:56Same sort of gnarled looking, beautiful...
0:11:56 > 0:11:59Have you named one after a supermodel or anything yet?
0:11:59 > 0:12:01I'm waiting!
0:12:01 > 0:12:04The couple believe individual crocodiles
0:12:04 > 0:12:06have distinct personalities.
0:12:07 > 0:12:11But they would never underestimate any of these creatures,
0:12:11 > 0:12:13least of all this one.
0:12:13 > 0:12:16(Look at the size of that crocodile there!)
0:12:17 > 0:12:20Mr T is a particularly aggressive male.
0:12:24 > 0:12:26CROCODILE HISSES
0:12:27 > 0:12:30- I don't know if you heard him, but he just hissed.- Yeah.
0:12:30 > 0:12:34So he's basically saying, "Look, don't get any closer."
0:12:34 > 0:12:37It's like a low level threat and his response.
0:12:37 > 0:12:43And if we did get too close to him, he might actually strike out at us.
0:12:44 > 0:12:48And the fact that it's staying still means that it's really brazen
0:12:48 > 0:12:49and confident.
0:12:49 > 0:12:54Usually they're really skittish and they disappear into the water.
0:12:54 > 0:12:55Look at those teeth.
0:12:58 > 0:13:00Crocodiles bask in the sun
0:13:00 > 0:13:03because they can't produce their own body heat like we do.
0:13:03 > 0:13:06They need to warm up to be active.
0:13:11 > 0:13:14- That was really quick. - That was like...
0:13:14 > 0:13:16That was like a gun, that's like a gun, isn't it?
0:13:16 > 0:13:21Look, there's no ripple, nothing. It's just disappeared under.
0:13:21 > 0:13:24We move away from this giant's patch
0:13:24 > 0:13:28and stop at a spot we think will be safe for my test dive.
0:13:30 > 0:13:32So how many dives have you done, Brad?
0:13:32 > 0:13:35Probably four, 500.
0:13:35 > 0:13:38Four, 500. Andy, are you about the same?
0:13:38 > 0:13:42Yeah, about... I would have said about 300.
0:13:42 > 0:13:44But that's Brad and I, we always have that issue.
0:13:44 > 0:13:46I've done 24.
0:13:46 > 0:13:49One of which was in a swimming pool in Chiswick, in West London.
0:13:49 > 0:13:52I don't think that actually technically counts.
0:13:52 > 0:13:56As lead safety diver, Andy is the one in charge.
0:13:56 > 0:13:59'But as the time approaches for me to go into the water,
0:13:59 > 0:14:01'I feel more and more vulnerable.'
0:14:01 > 0:14:03- And you have a hood? - I've got a hood, yeah.
0:14:03 > 0:14:06OK, are we about ready to go in?
0:14:06 > 0:14:09- No, no, no, no, I need my knife! - Oh, your knife!- My knife!
0:14:09 > 0:14:11Where are you going to put it?
0:14:11 > 0:14:13- On my calf, I think. - Probably the best place.
0:14:13 > 0:14:16Next to my right hand, so I can draw it quickly.
0:14:16 > 0:14:19Is that really going to actually do anything?
0:14:19 > 0:14:22Well, depends what you want doing. I don't know.
0:14:23 > 0:14:28'I'm hoping not to meet a crocodile this time.
0:14:28 > 0:14:32'But I need to know what to do, just in case.'
0:14:33 > 0:14:37We can't say there's not going to be a crocodile, there could well be a crocodile.
0:14:37 > 0:14:41In which case, it's going to be the worst of two scenarios, for you.
0:14:41 > 0:14:44You'll have the first time big current and the first time croc.
0:14:44 > 0:14:48What you have to avoid, Ben, at all costs,
0:14:48 > 0:14:50- is drifting onto that crocodile.- OK.
0:14:50 > 0:14:53- OK. That's why you've got a lot of weight on.- Yeah.
0:14:53 > 0:14:55If Brad gives the signal for crocodile,
0:14:55 > 0:14:57you have to grab something, you have to grab a branch,
0:14:57 > 0:15:02get onto the bottom and stay there, because we are going upstream, drifting with the current.
0:15:02 > 0:15:06If there's a croc lying downstream you can't drift onto it or over it.
0:15:06 > 0:15:08- That is a very dangerous position to be in.- OK.
0:15:08 > 0:15:13Either the crocodile's going to sit there, you're going to drift onto it and it's going to snap at something
0:15:13 > 0:15:16at a leg or... Or you're going to drift over it
0:15:16 > 0:15:20and it's going to see you as a silhouette which is, you know, could be a big fish,
0:15:20 > 0:15:25it could an animal on the surface floundering, which is what we want to avoid.
0:15:27 > 0:15:31'The idea of diving where there might be a crocodile seems crazy.'
0:15:31 > 0:15:33Nice and snug under your chin.
0:15:39 > 0:15:44The surface is the kill zone where crocodiles attack.
0:15:45 > 0:15:49'So I've been instructed to follow Brad and Andy to the bottom
0:15:49 > 0:15:55- 'as quickly as possible.' - OK, Ben. Three, two, one. In.
0:16:06 > 0:16:09'I've been told it's critical to stay on the river bed.
0:16:09 > 0:16:14'If I'm above a crocodile, it will see me as prey.
0:16:21 > 0:16:23It's kind of eerie
0:16:23 > 0:16:30as your eyes start adjusting to your underwater world.
0:16:32 > 0:16:36Shafts of light coming down.
0:16:36 > 0:16:38This is beautiful down here.
0:16:38 > 0:16:41It's like another world.
0:16:47 > 0:16:50'Brad and Andy only dive here during the winter months,
0:16:50 > 0:16:54'as crocodiles lose their appetite when the water is colder.
0:16:56 > 0:16:58'Visibility is also better at this time of year,
0:16:58 > 0:17:00'which means there's less chance
0:17:00 > 0:17:03'of bumping into a crocodile unexpectedly.'
0:17:11 > 0:17:16'As we swim out to the main channel, the current gets much stronger.
0:17:16 > 0:17:19'Beyond anything I've ever experienced.
0:17:20 > 0:17:22'I feel totally out of control.'
0:17:32 > 0:17:39'As we struggle with conditions, our worse-case scenario happens.'
0:17:42 > 0:17:44Oh! Oh, my God!
0:17:59 > 0:18:01Oh, that's too close!
0:18:05 > 0:18:07There it goes.
0:18:07 > 0:18:10Off into the gloom.
0:18:10 > 0:18:14'Brad and Andy believe one of the reasons that crocodiles don't attack
0:18:14 > 0:18:17'is because they see divers as other crocodiles.
0:18:19 > 0:18:22'But this test dive has gone way beyond what I expected,
0:18:22 > 0:18:25'and it's time for me to get out of the water.'
0:18:36 > 0:18:41I've never jumped out of the water so quickly in my life!
0:18:41 > 0:18:43Well, I didn't expect to see a crocodile then.
0:18:43 > 0:18:44There's a lot going on.
0:18:44 > 0:18:47The current is pushing you, the sediment is cloudy.
0:18:47 > 0:18:50- The croc was quite small and flighty. - Yeah.- Really young croc.
0:18:50 > 0:18:53It disappeared like that and that's even more disconcerting,
0:18:53 > 0:18:55cos it's like, "Where is it now?"
0:18:55 > 0:18:58The way it glides through the water and then it settled on the sand
0:18:58 > 0:19:01and you could see... I could see every colouration on it.
0:19:01 > 0:19:04And you could see its eyes just staring forward.
0:19:04 > 0:19:08It was beautiful. I never thought I'd say that about a crocodile,
0:19:08 > 0:19:11- but it was beautiful.- Did you feel in any danger around it?
0:19:11 > 0:19:15- How did you feel, was it comfortable?- I didn't feel comfortable, put it that way,
0:19:15 > 0:19:18but I felt reassured that these guys were around.
0:19:18 > 0:19:22You know, it's the first time I've seen one underwater like that.
0:19:24 > 0:19:27'It's very scary under there. But it's beautiful.'
0:19:27 > 0:19:32It's confronting your own fears and your own prejudices,
0:19:32 > 0:19:35cos I never thought I could even go into an African river,
0:19:35 > 0:19:37let alone one teeming with crocodiles.
0:19:49 > 0:19:51People in Botswana have no choice
0:19:51 > 0:19:54but to use these waters to make a living.
0:19:54 > 0:19:58And as the Okavango's crocodile population grows,
0:19:58 > 0:20:00attacks will increase.
0:20:04 > 0:20:08Nile crocodiles are opportunistic predators.
0:20:08 > 0:20:13They'll eat anything from fish to small hippos, wildebeest...
0:20:14 > 0:20:16..and people.
0:20:21 > 0:20:23'After 15 years of working with crocodiles,
0:20:23 > 0:20:27'Adam is well versed in how they attack.'
0:20:28 > 0:20:32We've all heard of the death roll. Does this thing exist?
0:20:32 > 0:20:35Yes, yes, and it's very well named.
0:20:35 > 0:20:39The croc's jaws are designed to clamp the body onto something.
0:20:39 > 0:20:42These things are like vices, and then the croc uses its body -
0:20:42 > 0:20:47its incredibly powerful, muscular body - then to rip things apart.
0:20:47 > 0:20:50And if it's on the surface, it'll flick its head,
0:20:50 > 0:20:54but if it's underwater, particularly if it's something large,
0:20:54 > 0:20:56they'll spin their body on the axis.
0:20:56 > 0:20:58And they can do this two or three times a second.
0:20:58 > 0:21:00And you imagine something grabbing onto your leg
0:21:00 > 0:21:05and spinning two or three times a second, it's impossible to do anything against that.
0:21:05 > 0:21:08Your leg is going to separate from your body.
0:21:10 > 0:21:13And what the crocodile will do is he'll grab you
0:21:13 > 0:21:15and then he'll take you down.
0:21:15 > 0:21:18And so you tend to drown.
0:21:18 > 0:21:22So you're usually dead before they start dismembering you.
0:21:24 > 0:21:28Everyone in the Okovango Delta knows someone who's been attacked.
0:21:30 > 0:21:35'I'm on my way to meet Retsi Sashama and her mother, Mrs Mangwe,
0:21:37 > 0:21:41'who know all too well the dangers of living near crocodiles.'
0:21:46 > 0:21:48Very nice to meet you, very nice to meet you.
0:21:48 > 0:21:51Hello. Hello, madam, hello. How do you do?
0:22:44 > 0:22:47What can you say when you see something like that?
0:22:47 > 0:22:51When two people's lives, a family, has been turned upside down.
0:22:51 > 0:22:54That is a statistic brought to life.
0:22:54 > 0:22:56For me, up until now,
0:22:56 > 0:23:00it's been the invisible side of the human-crocodile conflict.
0:23:00 > 0:23:04It's incredible that Retsi and her mother fought off a crocodile
0:23:04 > 0:23:05and lived.
0:23:10 > 0:23:14The long-term goal of our underwater research is to learn enough about
0:23:14 > 0:23:17crocodile behaviour, so that people know how to avoid being attacked.
0:23:21 > 0:23:26Tomorrow, Adam's going to attempt his first ever underwater tests
0:23:26 > 0:23:28on wild Nile crocodiles.
0:23:30 > 0:23:33If this pilot study is successful,
0:23:33 > 0:23:37it could open up a whole new method of researching crocodiles.
0:23:39 > 0:23:43Well, what I want to find out is what crocodiles are capable
0:23:43 > 0:23:45of perceiving when they're underwater.
0:23:45 > 0:23:49I'm hoping that we'll get some insight into that through some of these tests.
0:23:49 > 0:23:54'We'll be concentrating on key behaviours.
0:23:54 > 0:23:57'Where do they hide before attacking
0:23:57 > 0:24:00'and how do they detect prey from underwater?'
0:24:00 > 0:24:03- But the question is just how well can they see underwater?- So ideally,
0:24:03 > 0:24:06these balls, we're going to give to Ben to go
0:24:06 > 0:24:08and move past the croc?
0:24:08 > 0:24:11Oh, yes? I'm already working this out. To see the eye movement,
0:24:11 > 0:24:14you'll need to be very close underwater. Closer than we are now!
0:24:14 > 0:24:18You've got to remember that these are unpredictable,
0:24:18 > 0:24:21but they are also wild animals and dangerous. And you know that.
0:24:21 > 0:24:23And we don't want to push too far.
0:24:23 > 0:24:26The last thing I want is diver's mud prawning it in every direction
0:24:26 > 0:24:31because the croc finally thinks he's going to eat something.
0:24:31 > 0:24:34'The dive team head out to a channel filled with hippos,
0:24:34 > 0:24:35'known as the Filipo Channel.'
0:24:39 > 0:24:43If the research is go to ahead safely and successfully,
0:24:43 > 0:24:46Adam must rely on Brad and Andy's experience.
0:24:46 > 0:24:48There's no room for error.
0:24:50 > 0:24:57This is the first time I have consciously got in the water with...
0:24:58 > 0:25:02Certainly with a crocodile that was capable of killing me.
0:25:05 > 0:25:09If that guy that went in the water over there is anything to go by,
0:25:09 > 0:25:13this crocodile could give me a lot more than a nip if it bit me.
0:25:13 > 0:25:15Yeah, go. We'll see you down there.
0:25:16 > 0:25:20'The focus of Adam's dive is to test crocodile vision underwater.'
0:25:20 > 0:25:23- Ready, so keep the spike away from you.- OK.
0:25:23 > 0:25:27My job is to monitor the safety of the divers from the surface.
0:25:27 > 0:25:30OK, Adam. Surface to Mike, Adam is about to come in.
0:25:30 > 0:25:34Three, two, one... Adam in water.
0:25:42 > 0:25:46Watch the sediment when you get down.
0:25:46 > 0:25:48Going to get down pretty bad.
0:25:50 > 0:25:55Surface to Adam, do you copy, over?
0:25:59 > 0:26:04Surface to Adam. Do you copy, over?
0:26:07 > 0:26:10I can see their bubbles, they're crossing.
0:26:11 > 0:26:14'Even though I can see where the divers are, I can't hear them
0:26:14 > 0:26:16'clearly on the radio.
0:26:16 > 0:26:20'It's unnerving not knowing what's going on underwater.'
0:26:32 > 0:26:34'I think, let's get that boat...!'
0:26:34 > 0:26:37UNCLEAR SPEECH FROM RADIO
0:26:40 > 0:26:42Get the boat back.
0:26:42 > 0:26:46Surface to divers, yeah, copy that, will move out. Over.
0:26:56 > 0:26:59'Something has gone badly wrong.'
0:27:08 > 0:27:12'For top wildlife cameraman, Mike Pitts,
0:27:12 > 0:27:15'it's been one of the most terrifying experiences
0:27:15 > 0:27:17'of his career.' So it attacked you?
0:27:17 > 0:27:19Right from behind. It came right behind us.
0:27:19 > 0:27:24I had to use the camera. He got the bloody light in his mouth!
0:27:24 > 0:27:28- It bit me twice, you see the bite marks on the camera?- BLEEP.
0:27:28 > 0:27:32- Didn't bite you though, did he? - That was so scary!- Get this up here.
0:27:47 > 0:27:48BLEEP!
0:27:48 > 0:27:50I don't know how close he was,
0:27:50 > 0:27:54but I could see his ears and his teeth very clearly.
0:27:54 > 0:27:58And, oh, just this feeling that goes through you...
0:27:58 > 0:28:01If it wasn't for Andy I would have had it. I'm not joking.
0:28:01 > 0:28:04You realise that, for the first time,
0:28:04 > 0:28:07you're actually in the crocodile's environment.
0:28:07 > 0:28:09You're not in your own.
0:28:09 > 0:28:13And there was nothing I could do, I just thought, "OK, be calm."
0:28:13 > 0:28:16It came right up underneath Adam and Adam didn't see it.
0:28:16 > 0:28:20Came up to us, settled right underneath Adam and I just...
0:28:20 > 0:28:21I just pushed Adam out the way.
0:28:21 > 0:28:24It was 30 centimetres below him, watching him.
0:28:24 > 0:28:26I pushed Adam out the way, Mike then saw it,
0:28:26 > 0:28:29- put his camera on it and it just snapped.- Snapped on the camera.
0:28:29 > 0:28:31It went like that. It was ridiculous.
0:28:31 > 0:28:33We're spending too much time on the surface,
0:28:33 > 0:28:36which is enticing them to be predators.
0:28:36 > 0:28:39- It didn't look predatory to me, to be honest.- It looked territorial.
0:28:39 > 0:28:43- It looked like he was investigating us. He could've bitten me.- I mean,
0:28:43 > 0:28:46you've all got to get your breath, but is this the end of it?
0:28:46 > 0:28:50- This is the first interaction we've had like that.- Ever. In our lives.
0:28:50 > 0:28:53- We've never had anything like that. - And that's...hence the safety diver.
0:28:53 > 0:28:57- I can't watch what's going on behind me, yeah?- I was actually quite reassured by that,
0:28:57 > 0:29:02because my body immediately went into, "OK, safety crocodile mode."
0:29:02 > 0:29:05If I move quickly, it's going to bite me.
0:29:05 > 0:29:08- And I just let myself drift.- Turn around...- He was quite aggressive.
0:29:08 > 0:29:13'Adam's convinced the crocodile wasn't attacking.
0:29:13 > 0:29:15'He thinks it acted defensively
0:29:15 > 0:29:18'when startled by the sudden movement of Mike's camera.'
0:29:18 > 0:29:21It's all very well when you see Andy and Brad saying,
0:29:21 > 0:29:23"We've never seen that."
0:29:23 > 0:29:26- Well, they have now!- 2.7 metres.
0:29:26 > 0:29:29What Adam had to his advantage was that he knew to remain
0:29:29 > 0:29:32absolutely still. He didn't even talk into his mask.
0:29:32 > 0:29:34And I know I wouldn't have done that.
0:29:34 > 0:29:37I just know my instinct would have been to start finning away
0:29:37 > 0:29:40or to start talking, because I'm a presenter, it's what I do.
0:29:40 > 0:29:43I just start talking about my surroundings.
0:29:43 > 0:29:45And that's quite scary.
0:29:45 > 0:29:50Yeah, I was feeling as confident as you can get,
0:29:50 > 0:29:54and that's just thrown me completely,
0:29:54 > 0:29:59because it's just the safety brackets around it
0:29:59 > 0:30:02have just been stretched.
0:30:06 > 0:30:10'Today's incident was a harsh reminder that we're diving
0:30:10 > 0:30:12'with a dangerous animal.'
0:30:16 > 0:30:18It's also called into question
0:30:18 > 0:30:21whether it's safe enough to continue our expedition.
0:30:29 > 0:30:33'Everyone's had a night to reflect on what happened.'
0:30:34 > 0:30:37None of us want to risk an attack.
0:30:37 > 0:30:41But can we be sure that Brad and Andy's protocol for diving
0:30:41 > 0:30:44with crocodiles will keep us safe?
0:30:45 > 0:30:51Yesterday was a bit of a disastrous day all round in my eyes.
0:30:51 > 0:30:54So I'm a little concerned that maybe that trust has been breached.
0:30:54 > 0:30:59I don't think anything like that will happen again. If I thought it was likely to reoccur,
0:30:59 > 0:31:01we wouldn't be back in the water.
0:31:01 > 0:31:04We just need to learn to minimise the time on the surface.
0:31:04 > 0:31:07We need to actually streamline our whole process.
0:31:09 > 0:31:14I had kind of a slightly restless night's sleep.
0:31:14 > 0:31:16Just debating, you know, cos it's not...
0:31:16 > 0:31:20Everything yesterday just threw the balance out a little bit.
0:31:21 > 0:31:24And it is amazing what a night's sleep can do.
0:31:24 > 0:31:29I do feel clear minded and I do completely trust Andy and Brad.
0:31:29 > 0:31:33And that's the bottom line, I totally trust them.
0:31:33 > 0:31:37I go by human instinct and I will go in today.
0:31:37 > 0:31:40It doesn't make me any less nervous.
0:31:40 > 0:31:44I'm pooing myself, that's the only way to describe it.
0:31:45 > 0:31:47'We're all anxious.
0:31:49 > 0:31:52'So Brad suggests we head down the main channel to find
0:31:52 > 0:31:55'a female crocodile that he knows called Tutwana.
0:31:55 > 0:31:58'She might allow us close enough to study her.'
0:32:01 > 0:32:04'We speed up our entry into the water
0:32:04 > 0:32:07'to attract less attention at the surface.
0:32:09 > 0:32:13'Our aim is to pick up yesterday's research, observing the crocodile's
0:32:13 > 0:32:16'visual reactions underwater.
0:32:18 > 0:32:22'Adam has asked us to get close-up shots of the crocodile's eyes.
0:32:25 > 0:32:28'Within minutes, we find Tutwana.'
0:32:30 > 0:32:37I can't believe that just a couple of feet away from me,
0:32:37 > 0:32:40is a crocodile. A wild crocodile.
0:32:41 > 0:32:44I actually don't feel very comfortable when I've got my head
0:32:44 > 0:32:49turned away from it. I'm just going to have another little look.
0:32:49 > 0:32:50Look at those teeth!
0:32:52 > 0:32:56You can see them from a long way away.
0:32:56 > 0:32:59Those powerful, white teeth
0:32:59 > 0:33:04that they use for ripping their prey apart.
0:33:05 > 0:33:08Their teeth gleam bright white in the gloom.
0:33:10 > 0:33:13Crocodiles have a constant razor sharp supply.
0:33:13 > 0:33:16Each tooth is replaced every ten months.
0:33:16 > 0:33:19I am with it in its natural habitat.
0:33:19 > 0:33:23Something that very, very few people ever get to see,
0:33:23 > 0:33:25and I am petrified.
0:33:25 > 0:33:28I'm totally in Brad's hands here.
0:33:29 > 0:33:32'I follow Brad's diving protocol -
0:33:32 > 0:33:36'keep calm, stay tight to the bottom to avoid looking like prey
0:33:36 > 0:33:41'and keep out of striking range of her jaws.'
0:33:41 > 0:33:44I still feel I'm too close.
0:33:44 > 0:33:46Cos this looks huge.
0:33:46 > 0:33:48It's bigger than me.
0:33:49 > 0:33:54And you suddenly realise what power a creature like this must have.
0:33:54 > 0:33:56You'd be defenceless.
0:33:57 > 0:34:03'Amazingly, there's no sign that this crocodile will attack us.
0:34:03 > 0:34:04'Andy and Brad could be right.
0:34:04 > 0:34:08'Maybe it does think I'm just a small crocodile and no threat.'
0:34:08 > 0:34:13'Ben to surface, it's sitting on the bottom.'
0:34:13 > 0:34:16It's very relaxed.
0:34:16 > 0:34:18Sitting out of a current.
0:34:18 > 0:34:20Its eye looks glazed over.
0:34:22 > 0:34:25Ooh, it's just moving, one second.
0:34:25 > 0:34:27Oh, my God, this is so close!
0:34:30 > 0:34:32BEN GROANS
0:34:34 > 0:34:37Just went straight past my head!
0:34:39 > 0:34:40Just starting to move.
0:34:40 > 0:34:44I'm a bit worried it's going to come down towards us.
0:34:44 > 0:34:47I'm sure it's looking at us. It knows we're here.
0:34:49 > 0:34:53But I feel certain that it can tell it's being watched.
0:34:57 > 0:35:00So Ben just said that he was sure that the crocodile
0:35:00 > 0:35:01was looking at them.
0:35:03 > 0:35:05And, of course, it's hard to be certain,
0:35:05 > 0:35:09but this is one of the questions - how well can they see underwater?
0:35:09 > 0:35:11See, a lot of crocodiles live in really murky water,
0:35:11 > 0:35:14but this is crystal clear. So why would they not use vision?
0:35:14 > 0:35:17And they've got a transparent, nictitating membrane.
0:35:17 > 0:35:19There has to be a reason for that.
0:35:19 > 0:35:22They have to be able to see shadows and shapes.
0:35:22 > 0:35:24And I reckon this croc can see them moving close,
0:35:24 > 0:35:27but he probably doesn't quite know what he's looking at.
0:35:31 > 0:35:33My heart is pounding away.
0:35:34 > 0:35:37It's so near, it makes little movements.
0:35:39 > 0:35:41And it just looks like... Oh, here it goes,
0:35:41 > 0:35:44it's making a move in front again.
0:35:46 > 0:35:47Oh!
0:35:48 > 0:35:50Holy crap!
0:35:50 > 0:35:56Sorry, that's not very scientific, but that's how you feel.
0:35:56 > 0:36:02Crocodiles don't have gills. They breathe air like us.
0:36:02 > 0:36:06They can slow their heart rate down to just a few beats an hour,
0:36:06 > 0:36:11which helps them to stay underwater for more than 45 minutes at a time.
0:36:11 > 0:36:14Just edging closer and closer.
0:36:14 > 0:36:17I can see her tail really close.
0:36:17 > 0:36:21And her scutes, as they keep describing them,
0:36:21 > 0:36:25which is how they identify one crocodile from another.
0:36:30 > 0:36:34This has got to be one of the most extraordinary encounters
0:36:34 > 0:36:38I have ever had.
0:36:38 > 0:36:42Look how close! I feel I could just reach out and touch her.
0:36:42 > 0:36:46I could! Oh, it's moving off slowly.
0:36:46 > 0:36:48Off into the gloom.
0:36:49 > 0:36:55Well that was properly my first crocodile encounter.
0:36:55 > 0:36:57I'm actually shaking.
0:36:59 > 0:37:01Um...
0:37:01 > 0:37:04It's difficult to describe what it's like.
0:37:04 > 0:37:08What you have to remember is this is a wild creature in its wild habitat,
0:37:08 > 0:37:11and it accepted us here.
0:37:11 > 0:37:14It's truly extraordinary.
0:37:33 > 0:37:35- Woah, thanks.- Well done.
0:37:35 > 0:37:37OK, that's fine, you can do the other side.
0:37:37 > 0:37:38It's incredible.
0:37:38 > 0:37:40So close.
0:37:40 > 0:37:43Really scary, but magical.
0:37:43 > 0:37:48We followed it for about, probably, about 10, 15 minutes, really.
0:37:48 > 0:37:51And, uh, amazing.
0:37:51 > 0:37:53My heart's still pounding.
0:37:56 > 0:37:58Thanks, Brad.
0:37:58 > 0:38:02- A lovely little interaction, huh? Lovely little croc.- Incredible!
0:38:02 > 0:38:05You see how amazing, how they sit? When you get really close to them?
0:38:05 > 0:38:09They're aware of you, but they don't panic. They're not, you know...
0:38:09 > 0:38:12The one bit where it turns and kind of started coming towards me...
0:38:12 > 0:38:15But you said that it might do that and I just stayed still,
0:38:15 > 0:38:18so it's just about playing by those rules that you've set in place.
0:38:23 > 0:38:25I can go so far as to say that was the scariest thing
0:38:25 > 0:38:28I've ever had to do. Without question.
0:38:29 > 0:38:33I'm really proud that I was able to overcome those fears.
0:38:33 > 0:38:35And those fears were partly based on prejudices that I had
0:38:35 > 0:38:39about crocodiles. Those fears that are ingrained in all of us,
0:38:39 > 0:38:43that crocodiles equal death.
0:38:43 > 0:38:47I hope that I'm getting a small insight into
0:38:47 > 0:38:50a misunderstood creature.
0:38:57 > 0:38:59Adam reviews the day's footage.
0:38:59 > 0:39:02Oh, and that... Just beautiful.
0:39:02 > 0:39:07This is just remarkable. I can't believe what I'm seeing, actually.
0:39:09 > 0:39:13It's offering tantalising clues as to how crocs may achieve
0:39:13 > 0:39:15underwater vision.
0:39:15 > 0:39:21One of the theories I had was that the nictitating membrane
0:39:21 > 0:39:24was basically acting like a contact lens.
0:39:24 > 0:39:28The nictitating membrane protects the crocodile's eyes when submerged.
0:39:28 > 0:39:34But Adam has never been 100% sure how well they can see through it.
0:39:34 > 0:39:39I mean, that eye, that nictitating membrane looks so clear.
0:39:39 > 0:39:42Sometimes when you actually see it from a different angle,
0:39:42 > 0:39:45it's got an almost pearlescent look to it.
0:39:45 > 0:39:48The footage is helpful, but not conclusive.
0:39:48 > 0:39:50And Adam wants to know more.
0:39:59 > 0:40:02Almost a week into the expedition, and Adam's preparing
0:40:02 > 0:40:06to introduce some interactive props to our research.
0:40:08 > 0:40:12He's developed his own close vision test.
0:40:12 > 0:40:16This is actually a multi-function, data acquisition device.
0:40:16 > 0:40:20So there's marks on here at one-foot intervals,
0:40:20 > 0:40:22so hopefully I can measure the animal's tail
0:40:22 > 0:40:25and get some idea of its total length.
0:40:25 > 0:40:28And then this, we're going to be using for the vision test.
0:40:28 > 0:40:32So I'll actually pull this off so I can extend this out
0:40:32 > 0:40:37and the aim is to actually push this to the side of the crocodile's head
0:40:37 > 0:40:38and see whether it responds.
0:40:38 > 0:40:41See whether it can see it at a certain distance from the head
0:40:41 > 0:40:43and at a specific angle.
0:40:45 > 0:40:48This is an important moment for Adam.
0:40:48 > 0:40:53His close vision test has never been undertaken on a wild crocodile.
0:41:06 > 0:41:11He selects his first test subject and sizes it up.
0:41:12 > 0:41:16A croc's length is roughly double its tail,
0:41:16 > 0:41:18making this one three metres long.
0:41:21 > 0:41:24Next, Adam conducts his vision test,
0:41:24 > 0:41:28carefully extending his pole towards the crocodile's eyes
0:41:28 > 0:41:31to see at what point it will respond.
0:41:49 > 0:41:51The sight test is a success.
0:41:51 > 0:41:57But then something happens that none of us had anticipated.
0:42:00 > 0:42:03The croc makes off with the equipment,
0:42:03 > 0:42:05pulling Adam in its wake.
0:42:08 > 0:42:12It behaves more like a dog with a bone than a killer.
0:42:14 > 0:42:17Adam lets go and, moments later,
0:42:17 > 0:42:21the croc reappears with what looks uncannily like a smile.
0:42:30 > 0:42:34It heads for the surface to breathe, clutching its new toy.
0:42:49 > 0:42:51Oh, boy!
0:42:51 > 0:42:53Yeah?
0:42:53 > 0:42:55How was that?
0:42:55 > 0:42:58- That was worth the wait!- Oh, was it?
0:43:02 > 0:43:05Well, is it going to react?
0:43:06 > 0:43:11What do you reckon the result of that test was?
0:43:11 > 0:43:13Definitely a positive result.
0:43:13 > 0:43:16- And that's why...- I've got a shot of him, he's going down the thing
0:43:16 > 0:43:20- with a fishing rod. At the end there's this croc pulling him! - I'm glad you're all laughing!
0:43:20 > 0:43:23He's actually got the croc on the end of the stick!
0:43:23 > 0:43:24He's swimming around like...
0:43:24 > 0:43:28I thought, "If I can just brace myself, then he'll pull it off."
0:43:28 > 0:43:30And I did and he eventually pulled it off.
0:43:30 > 0:43:33Then he started swimming along with this polystyrene ball in his mouth.
0:43:33 > 0:43:36- See what he did immediately? - Straight to the surface.
0:43:36 > 0:43:39- Straight to the surface, so he can crunch it and swallow it.- Yeah.
0:43:39 > 0:43:44- They have to surface to do it and he went straight up. - What that showed me, quite clearly,
0:43:44 > 0:43:48there's absolutely no doubt that the crocodile can see underwater.
0:43:48 > 0:43:52I deliberately moved the ball gradually into its field of vision.
0:43:52 > 0:43:55And it didn't respond at all,
0:43:55 > 0:43:58until it got to directly perpendicular with the head.
0:43:58 > 0:44:02At that 90 degree angle, suddenly the crocodile's head moved.
0:44:02 > 0:44:05So yeah, I'm in absolutely no doubt about it at all.
0:44:05 > 0:44:07That crocodile, at a distance of
0:44:07 > 0:44:10probably about 80 centimetres,
0:44:10 > 0:44:13could detect that white object in the water.
0:44:13 > 0:44:16There it is, right at the end of the channel.
0:44:19 > 0:44:21Adam retrieves the ball gingerly,
0:44:21 > 0:44:25'in case the crocodile is still close by.' Well retrieved.
0:44:25 > 0:44:29There you go. Remarkably little... Remarkably few bites in that.
0:44:29 > 0:44:33So as she tried to crush it, she bit it and then spat it out, basically.
0:44:33 > 0:44:36We're beginning to build up a fascinating picture
0:44:36 > 0:44:38of how crocodiles sight their prey.
0:44:40 > 0:44:43But not everybody shares our enthusiasm for these
0:44:43 > 0:44:45incredible animals.
0:44:48 > 0:44:50'Given the number of attacks in the delta,
0:44:50 > 0:44:53'it's hardly surprising that most locals here
0:44:53 > 0:44:58'see crocs as a deadly threat that they'd rather be rid of.
0:44:58 > 0:45:01'The fact that they're a protected species is something many locals
0:45:01 > 0:45:04'are at a loss to understand.'
0:45:04 > 0:45:07- Vince, hey there.- How're you doing? - How are you? Good to see you.
0:45:07 > 0:45:11- Are you well?- Very well, very well. - Thanks for this.- No worries at all.
0:45:11 > 0:45:14Our ecologist, Vince Shacks, is keen to teach that crocodiles here
0:45:14 > 0:45:17are protected for a very good reason.
0:45:19 > 0:45:20OK, good morning, everybody.
0:45:20 > 0:45:22- ALL:- Good morning.
0:45:22 > 0:45:25Today we're here to talk to you about crocodiles.
0:45:25 > 0:45:30How many of you have seen a crocodile in the river before?
0:45:30 > 0:45:32That's everybody has seen crocodiles.
0:45:32 > 0:45:34The river here is very healthy.
0:45:34 > 0:45:37We've got lots of fish, we've got clean water,
0:45:37 > 0:45:40we've got lots of crocodiles, we've got lots of bream.
0:45:40 > 0:45:42So everything is working very, very well,
0:45:42 > 0:45:45because every one of the food chain is there today.
0:45:46 > 0:45:49'The crocodile is a key predator in the Okavango Delta.
0:45:49 > 0:45:52'Its main source of food is the catfish, or barbel
0:45:52 > 0:45:55'which, in turn, eats the smaller bream -
0:45:55 > 0:45:58'an important fish for the local people.'
0:45:58 > 0:46:00So if take the crocodile out...
0:46:00 > 0:46:02Less crocodiles mean more barbels.
0:46:03 > 0:46:06So if there's more barbel, there's less bream,
0:46:06 > 0:46:08so now the bream are going to disappear.
0:46:08 > 0:46:11All the fish that we like to eat, that taste very nice,
0:46:11 > 0:46:13are now going to disappear.
0:46:15 > 0:46:18OK.
0:46:18 > 0:46:20Very nicely.
0:46:20 > 0:46:23And a lot of these kids will have grown up, probably
0:46:23 > 0:46:26- being told by their families... - Absolutely.
0:46:26 > 0:46:29..warned about crocodiles. Probably seeing them as a pest.
0:46:29 > 0:46:32Yes. No, no, definitely. Almost certainly, you know?
0:46:32 > 0:46:34So we want to get that message across that there's
0:46:34 > 0:46:37a little bit more to them.
0:46:37 > 0:46:40But the hard truth is, at some point in their lives,
0:46:40 > 0:46:43most of these children will know someone who's been attacked
0:46:43 > 0:46:45by a crocodile.
0:46:45 > 0:46:48What do you think?
0:46:48 > 0:46:49Rough. Rough here.
0:46:49 > 0:46:53But have you felt underneath? Try feeling the belly. Woah!
0:46:56 > 0:47:01It is a bit confusing, in my mind, where you draw the line
0:47:01 > 0:47:06between conservation, protection, understanding.
0:47:06 > 0:47:09But the more I spent time here, the more I feel convinced
0:47:09 > 0:47:12that the more we understand about the crocodile,
0:47:12 > 0:47:15the better we can have that harmony.
0:47:20 > 0:47:24Back at base, Adam reviews today's footage.
0:47:24 > 0:47:27He's increasingly curious about where crocodiles choose
0:47:27 > 0:47:30- to lie in wait. - Sometimes, they'll strike.
0:47:30 > 0:47:31- They've sort of got a bolthole.- Yeah.
0:47:31 > 0:47:34They'll move from the basking site a little bit up or down.
0:47:34 > 0:47:38It's almost like a cave, underneath, that's cut out under the bank,
0:47:38 > 0:47:39isn't it?
0:47:39 > 0:47:44Adam really wants to find out why a crocodile chooses a certain patch.
0:47:44 > 0:47:46Is it to do with the water temperature?
0:47:46 > 0:47:49Is it to do with the strength of the current,
0:47:49 > 0:47:51is it to do with the sunlight coming through?
0:47:51 > 0:47:54The crocs that we see regularly, go to the same places.
0:47:54 > 0:47:57To me, that's a really interesting question. What is it about
0:47:57 > 0:48:00these places that these crocodiles are finding comfortable?
0:48:00 > 0:48:02Why are they moving there?
0:48:02 > 0:48:06Understanding where and why they hide will give us
0:48:06 > 0:48:09a better idea of where they might attack.
0:48:17 > 0:48:19I can write underwater with this thing.
0:48:19 > 0:48:22I'm going to take some temperature measurements around the crocodile
0:48:22 > 0:48:26and I'm also going to actually try and get a light meter recording
0:48:26 > 0:48:28where the crocodile's resting.
0:48:31 > 0:48:33Over the next few days,
0:48:33 > 0:48:36Adam and I submerge into his underwater laboratory.
0:48:40 > 0:48:43We're testing both the main river channel
0:48:43 > 0:48:47and caves under the bank to see which spots crocodiles prefer.
0:48:47 > 0:48:50If you could get a water temperature reading on the croc
0:48:50 > 0:48:53and just let me know over comms and I'll just write it down here.
0:48:53 > 0:48:54- That'll be great.- OK.
0:48:54 > 0:48:57- Just clip it on somewhere that'll be easy to see.- Yep.
0:48:57 > 0:48:59Go.
0:49:02 > 0:49:05We take measurements of current speed,
0:49:05 > 0:49:08light levels and water temperature.
0:49:09 > 0:49:13This way we can establish their ideal environment.
0:49:16 > 0:49:20It appears crocodiles prefer sheltered caves
0:49:20 > 0:49:23which are warmer than the open water.
0:49:23 > 0:49:28We also discover that crocodiles are less likely to be found in areas
0:49:28 > 0:49:29with strong currents -
0:49:29 > 0:49:34vital information to those living on the river.
0:49:34 > 0:49:36If you're looking at it from the perspective of someone
0:49:36 > 0:49:39who was coming down to the water, if there was a really flat,
0:49:39 > 0:49:42fast-flowing, deep channel directly beneath you,
0:49:42 > 0:49:46there would actually be a lot less chance of there being a crocodile
0:49:46 > 0:49:50down there, compared to a much more open channel where the flow rate is a lot less.
0:49:56 > 0:50:00Winter here is coming to an end.
0:50:00 > 0:50:04As the water warms up, crocodiles will become more interested
0:50:04 > 0:50:08in feeding, making it too dangerous to dive.
0:50:08 > 0:50:13'So today is our last chance to work with these crocodiles this year.'
0:50:15 > 0:50:17Last day.
0:50:17 > 0:50:21Strange. It's amazing how, if I think back to those first few days,
0:50:21 > 0:50:25you know, it was so terrifying.
0:50:25 > 0:50:28And now, I'm actually quite sad that this is my last dive.
0:50:28 > 0:50:32I'd love to go out with one final, amazing encounter.
0:50:32 > 0:50:35And all my fingers.
0:50:38 > 0:50:41So far on this expedition we've achieved most of what
0:50:41 > 0:50:42we set out to do.
0:50:44 > 0:50:46We had one close call,
0:50:46 > 0:50:50but we've also made some groundbreaking discoveries.
0:50:57 > 0:50:59We have one last aim -
0:50:59 > 0:51:02to find out whether the larger and more dominant crocodiles
0:51:02 > 0:51:07in the area, will tolerate our presence in their lairs.
0:51:12 > 0:51:16We go in search of a giant crocodile that Brad calls Mawasi -
0:51:16 > 0:51:20a Botswanan word for "scaled creature."
0:51:28 > 0:51:32It doesn't take long to find him in his lair.
0:51:32 > 0:51:34It knows we're here.
0:51:36 > 0:51:38But it's putting up with us.
0:51:41 > 0:51:47The reality is, this could kill me instantaneously.
0:51:48 > 0:51:50And it's terrifying for that.
0:51:52 > 0:51:55This is the biggest crocodile I've ever seen.
0:51:55 > 0:51:58I estimate it's probably four metres.
0:51:59 > 0:52:03'This huge crocodile has been defending its territory
0:52:03 > 0:52:05'its whole adult life,
0:52:05 > 0:52:08'yet doesn't react to me at all.'
0:52:08 > 0:52:11I mean, a big three-and-a-half, four metre crocodile is way overkill
0:52:11 > 0:52:13in terms of being able to kill you.
0:52:13 > 0:52:17Definitely. They're capable of dealing with large mammals
0:52:17 > 0:52:18and, I mean, we're just a snack.
0:52:21 > 0:52:24Ah, there it goes.
0:52:38 > 0:52:43'It moves so effortlessly, so beautifully.
0:52:43 > 0:52:44'Since I've been here,
0:52:44 > 0:52:49'I've discovered that crocodiles walk underwater, rather than swim -
0:52:49 > 0:52:53'a clever and most graceful way to conserve energy.'
0:52:54 > 0:52:59I'm really beginning to see a different side of crocodiles now.
0:52:59 > 0:53:05Terror is turning into a sort of fascination.
0:53:05 > 0:53:06I'm still scared...
0:53:07 > 0:53:10..cos this is a wild creature.
0:53:17 > 0:53:19I'm actually quite jealous right now.
0:53:19 > 0:53:21I would love to be down there right now...
0:53:21 > 0:53:25actually seeing this crocodile, as well.
0:53:25 > 0:53:29But I think this is pretty much establishing that you can get
0:53:29 > 0:53:34in the water with these crocodiles, and as long as the circumstances
0:53:34 > 0:53:37are right, the crocodile's just not bothered.
0:53:43 > 0:53:48I'll never quite look at crocodiles the same way again.
0:53:56 > 0:54:00Still looking forward to getting back into that boat, though!
0:54:15 > 0:54:16Absolutely huge!
0:54:16 > 0:54:20It'll be interesting to hear what Brad's estimation was.
0:54:20 > 0:54:25Probably four metres. Maybe I'm doing a typical male thing,
0:54:25 > 0:54:29saying it was bigger than it was, but honestly, I was like this...
0:54:29 > 0:54:31to its tail. Just there.
0:54:31 > 0:54:34Did you resist the temptation?
0:54:34 > 0:54:36- I got close enough. - I'm very glad that...
0:54:36 > 0:54:39- Thank you. And I'm so... - ..I've changed your perceptions.
0:54:39 > 0:54:44..proud to have been part of all of this. Thank you, that was... How big do you think that was?
0:54:44 > 0:54:47- I said four metres.- It's definitely over three.- Over three.
0:54:47 > 0:54:50- Definitely over three metres. - Probably nearly four!
0:54:50 > 0:54:54'Our pilot study has been a success and has opened the door
0:54:54 > 0:54:57'to a revolutionary new way of researching wild crocodiles
0:54:57 > 0:54:59'in the future.
0:54:59 > 0:55:02'We've shown they can be studied underwater.
0:55:02 > 0:55:06'And we now have a better understanding of their vision
0:55:06 > 0:55:08'and where they hide.
0:55:08 > 0:55:11'We've found that, underwater, crocodiles avoid
0:55:11 > 0:55:17'fast-flowing currents, so those areas are safer for local people.
0:55:17 > 0:55:20'We've also learned that if you do encounter a crocodile in the water
0:55:20 > 0:55:22'and can't get away,
0:55:22 > 0:55:26'diving to the bottom might be the safest thing to do.'
0:55:26 > 0:55:30As a scientist, the most exciting thing, for me,
0:55:30 > 0:55:35is the fact that there's a new opportunity to collect data in a way
0:55:35 > 0:55:37that's never been done before.
0:55:37 > 0:55:44We can start to really ask questions that haven't been asked before.
0:55:44 > 0:55:46If this is how crocodiles are behaving underwater,
0:55:46 > 0:55:49how can we modify our behaviour,
0:55:49 > 0:55:53so that we can make it safer for people who live around crocodiles?
0:56:01 > 0:56:05It's been an incredible journey.
0:56:05 > 0:56:09You know, I've seen so much, I've learned so much along the way.
0:56:09 > 0:56:12I've obviously seen the sharp end of crocodiles,
0:56:12 > 0:56:15I've seen that they can be killing machines and the effect
0:56:15 > 0:56:19that they have on people who have to live alongside them.
0:56:19 > 0:56:22Thank you so much. It's been...
0:56:22 > 0:56:25'But I've also seen that they're misunderstood creatures.
0:56:25 > 0:56:29'And maybe some of this research might change that relationship
0:56:29 > 0:56:31'between crocodile and man.'
0:56:31 > 0:56:34It's been amazing! Really, really amazing.
0:56:34 > 0:56:38- Oz next.- Australia next.- We'll see you in Australia in a few weeks.
0:56:42 > 0:56:44Well, he survived.
0:56:46 > 0:56:48Good thing, too!
0:56:51 > 0:56:56'Next time, we face a very different underwater challenge...
0:56:56 > 0:56:59'Australia's salt water crocodile.
0:57:01 > 0:57:04'The largest...'
0:57:04 > 0:57:05Her back leg, sorry.
0:57:05 > 0:57:08'..and most aggressive reptile on earth.'
0:57:08 > 0:57:11Back, back, back, back, back!
0:57:11 > 0:57:12This is crazy!
0:57:12 > 0:57:17'No scientist has ever dived with a wild saltwater crocodile before.'
0:57:17 > 0:57:20Why is he opening his mouth now and looking at me?
0:57:20 > 0:57:22Is he about to launch up?
0:57:22 > 0:57:25Quite frankly, it's a terrifying prospect at this moment.
0:57:46 > 0:57:50Subtitles by Red Bee Media Ltd