Of all the fish in all the world's waters, the piranha may have the worst reputation. One look at this predator's razor-sharp teeth and powerful jaws is enough to send chills up anyone's spine. Although it's known worldwide for its aggressive feeding behavior, the piranha is only found throughout the fresh waters of South America. They typically feed at dawn and dusk, lurking in the water and waiting for a small animal to pass by. Then, without warning, they attack and devour their prey with impressive ferocity. Sometimes they even form terrifying hunting groups in order to take down much larger prey, including horses, capybaras or even humans.