A deep-bodied, omnivorous, freshwater fish (family Characidae), up to about 60 cm long, that has a very strong bite and very sharp, triangular teeth. Piranhas occur in rivers in the Amazon Basin and have also been discovered elsewhere, probably as escapes from aquaria. They swim in shoals for protection from their own predators. Piranhas do bite humans, usually on the fingers or toes, and can be aggressive in the dry season when river levels are low and the fish are hungry, but they are less aggressive than their reputation suggests, and many are scavengers. There are three–five genera and 30–60 species.