A half-ton tiger and lion hybrid. A 55-pound salamander. A spider the size of a dinner plate. And a giant beach worm. In nature, some living creatures are so unique, they?re in a class by themselves. Fearsome fighting machines. Speed demon predators. Behemoths of the deep. So extraordinary, they seem almost impossible. So baffling, they fill us with wonder. How do these remarkable animals do what they do? We meet experts who research the species in question and unlock their secrets in the quest for the world?s most Unbelievable Beasts.