A piranha's natural habitat includes the Orinco, Guyana, Amazon, Rio Sao Francisco, Rio Paraguay and Rio Parana rivers in South America. These rivers have temperatures between 75 and 86 F and carry fine particles in suspension, giving them a milky-white appearance known as whitewater.
Piranhas exist in the rivers of South America largely due to a phenomenon called the Pororoca. The rivers lie at a higher relief than the ocean. The ocean waters push against the fresh river waters until the pressure explodes with giant waves. The Pororoca kills a large number of animals and leaves the perfect feeding ground of cadavers for the piranha.