Herpetologist Vince Shacks and underwater cameraman Brad Bestelink go on a unique crocodile diving adventure to find out more about these cave systems, and how the reptiles use them. They enter a dark underworld of mystery and danger, and they find themselves doing things that no one has ever attempted before. Apart from swimming with huge crocodiles, they're the first to noose a wild Nile crocodile underwater, and they're the first to attach a remote camera to it, to see where it goes.