It's the astounding world of monster fish with monster teeth. Sporting mega-mouthfuls of razor-sharp weapons - they chomp, shred, slash and slice. What began with the prehistoric, 40-ton Megalodon - with teeth the size of meat cleavers - lives on today in toothy super-species, from sharks to Brazil's mysterious Payara, AKA 'Vampire Fish.' Reeling them in is a knockdown, no-holds-barred fight to the finish. And one intrepid ichthyologist's Amazon expedition to study them is the ultimate adventure.