One hundred miles from Australia's north coast, the Yellow Waters and the South Alligator Rivers cut through an ancient limestone plateau to crate Kakadu National Park. This is a rich natural world where nature has sculpted rainforest niches and deep gorges that fill with wild rivers each monsoon season. In the rivers, up the creeks and on the shores, the saltwater crocodile swims, hunts and lay eggs. Living alongside this giant prehistoric reptile are wallabies, pig-nosed turtles, king brown snakes, water lizards and hundreds of species of brightly colored birds. (60 minutes)