Vâgner treks deep into the Amazon in search of a river monster essentially unchanged since the Jurassic age -- the arapaima. These massive predators can eat just about anything, even snatching up birds and monkeys from the water's surface! It's a grueling expedition, but after days in the jungle's extreme environment, Vâgner reels in the biggest arapaima he's ever seen. It's a 10-foot-long specimen, measuring nearly 5 feet in girth and weighing a whopping 325 pounds! (Source: National Geographic Channel)