Next airing Sat Dec 5, 4 p.m. ET

Croc Invasion

Australia's Crab Island is a far cry from the laid-back world of the Great Barrier Reef. Here, it's a crocodilian battleground. Where rivers provide year-round food, one of the world's largest and fiercest predators, the saltwater crocodile, lurks, waiting for its prey. But it's not all about hunting for these beasts; it's also about protecting their territory -- both their food and their females. That means they'll fight any beast to keep what's theirs ... even if it's one of their own kind.