The following script is from "The Nile Crocodile" which aired on March 24, 2013. Anderson Cooper is the correspondent. Michael Gavshon and Paul Bellinger are the producers.
Of all the different species of crocodiles in the world, Africa's Nile crocodile is the most dangerous and deadly. They can grow up to 20 feet long, weigh as much as a car, and bite as hard as a Tyrannosaurus Rex. Crocodiles are prehistoric creatures that have been around since the time of dinosaurs, but we still don't know a lot about them because studying them up close on land is treacherous, and underwater has always thought to be impossible. Now two wildlife filmmakers in Botswana in Southern Africa have found a way to get up close to crocs in the murky water of the Okavango Delta. The images they've captured are some of the most remarkable wildlife scenes we've ever seen.
The Okavango Delta has been called one of the last Eden's on earth. The hundreds of miles of winding waterways and untouched islands are home to some of Africa's most exotic and enchanting wildlife. It's also home to thousands of Nile crocodiles. For the last five years, Brad Bestelink and his wife, Andy Crawford, have been risking their lives filming these man-eaters in the most daring way imaginable: following the crocodiles into their underwater lairs.
It is a dark and foreboding world down there, visibility is sometimes only a few feet and you can't even see the crocodiles until you catch a glimpse of their long rows of razor sharp white teeth.
Anderson Cooper: How did you know you could do this?
Brad Bestelink: We were next to a ledge. And this crocodile swam out. And actually swam between us. And then settled on the ground next to us.
Anderson Cooper: What first went through your mind?
Andy Crawford: Well, just lots of bubbles?
Brad Bestelink: Bubbles.
Andy Crawford: And just panic.
The panic was understandable. Nile crocodiles are Africa's largest and most feared predator but surprisingly this one didn't attack. Brad and Andy have been getting closer and closer to these creatures ever since.
Brad Bestelink: You do get a different sense of them. They look very beautiful underwater. They're dappled and gold and black. And you see them as more timid I think. Beyond the teeth and the terror there's this incredible creature that is actually an amazing animal in its own right.
Anderson Cooper: You actually think they're beautiful.
Andy Crawford: I do think they're beautiful. I never used to think they were beautiful. But this is a whole different view of them.
This is the view most people have of Nile crocodiles. Patient and stealthy killers, they grab their prey, drag them into the water then drown and dismember them. And it's not just animals they eat, hundreds of people in Africa are killed each year while bathing, laundering clothes, or fishing along the waters' edge.
Nile crocodiles are now protected in Botswana, but Brad and Andy believe more needs to be known about their behavior in part so that humans can better avoid them. They've invited Dr. Adam Britton, an Australian zoologist, to dive with them.
Anderson Cooper: When you first heard about what they were doing here, what did you think?
Adam Britton: Look, I'll be honest. When I first heard about this, my instant, immediate reaction was "That sounds crazy."
Doctor Britton has been studying crocodiles for more than 18 years.
Adam Britton: I describe crocodile like Ferraris. They're just extremely finely honed creatures. They are just perfectly adapted to do what they do. They're, you know, the smartest of all the reptiles.