Never-Before-Seen Underwater Croc Dens

Nat Geo WILD captures footage of crocodiles swimming through secret tunnels.
5:34 | 01/13/12

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Transcript for Never-Before-Seen Underwater Croc Dens
-- -- also at home in the main force to watch chips in their natural habitat. Charles Darwin traveled to the Galapagos Islands and observe new species of birds. But -- go to study some of the world's deadliest crocodiles when they happen to live in pitch black underwater oil water finals well. You guessed it in my co anchor Bill Weir for our series into the one. Some endeavors are scared -- what others are -- -- Blatter. Greatest fears. And nothing combines plus triple. Darkness potential drowning and real monsters and play like scuba diving with crocodiles and let's let the business -- on -- -- the smile in the darkness. McCracken -- false and the last thing is not -- The -- of -- delta is one of the most beautifully lush corners of African teeming with life and for the people -- lived on these banks for millennia. This apex predator is a particular source of -- People. Get eaten they lose limbs. People do get a -- just upstream as the lady. His missing and on. And she went into risky to -- he lost but the wrong. Says that happen. Upset a witch doctor legend has it and he'll send a crock -- -- -- experts underwater lair. For beneath all this floating papyrus is a vast elaborate channels -- -- And for generations scientists wonder just how the Nile croc navigates. Hunts and drives down in this hidden world. And then nature photographer Graham -- and his colleagues realized. There's only one way to find out if you -- Tomlinson. You all didn't. Help him get off -- but you -- -- them and that's true. -- on the surface of comes federal food bank to -- -- I think that's. This year's -- -- happening now you'd be wrong. It's obviously just down into their instant and that's what they do that is Huntington -- they discovered this sink to the bottom trick. Grahame and his team -- able to capture the first ever images of the breathing crock. From below what I always thought to implement flat on the surface but his body was wrong down more. Yeah apparently than in the organs to just the Bruins -- The team and they wanted to get back then images that stood on the nation of this down and -- it blends together and wondering. And before then I've never seen. -- that it's almost comical way they've Bob spread eagle and then free -- -- first. But there's nothing funny about a close pass from that police got -- -- -- But it doesn't strike out. One possible reason -- have lousy underwater vision. The team discovers that the membrane that protects their eyes also clouds their eyesight. So instead they hunt mostly by feel. The new knowledge emboldens the team to try something much more ambitious than capturing -- Perfect colleges Vince shacks once the -- -- twelve foot adults and mount a -- cam to better understand their secret lives. Understand what -- reaction on intellectual functions -- so when he comes up we got an office in the custody electric company's principal. First attempt shows just how nimble these prehistoric mosquitoes can -- just slipping past open news. They're more successful with -- -- fifteen footer. But it proves to be too much crock. It's your fault it's terrifying the rope burns their hands and they're forced to give. But eventually they find one of semi and manageable size. Currently there's no real handbook for pulling -- -- -- -- and your votes -- they make do with a towel at some muscle. As a report valuable -- -- Prospect of getting the first -- cam pictures every quarter. Cameras designed to record for a couple of weeks and then -- -- But after a few minutes the signal disappears as stressed -- -- in decades. They decide to swimming and after. Past the shafts of light. Passed a foreboding pile of antelope bones. Into the murky blackness. You're overcoming to have maybe the biggest movies -- Being eaten. And claustrophobia what's -- like. -- -- -- that cost the woods isn't designed for really. You know looking through the camera and saves you kind of remove yourself from the suggestion. Concentrating on -- -- and every -- and again. Have a cup type stuff where I am powerful -- freaking -- he got to -- Angela -- -- look -- him. In the caves off sometimes that's left. You dispute that Thanksgiving courts and resolve -- home after. That you've touched upon he and -- not -- -- turnaround and then not slots opening that was behind he's gone. And you know you feel billions of that in and -- -- on the Rockland. -- -- In -- history. Forget the crocodile. Well I'm glad my pal bill stayed in the book. -- -- premieres this Sunday on Nat geo wild.

This transcript has been automatically generated and may not be 100% accurate.

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