Once upon a time, there was an earthquake that caused the floor of a lake to split. And through that seismic crack entered what was later identified as a group of prehistoric piranhas. All of that happened in the first movie, Piranha 3D, which went on to become a hit with its blood, violence, and skin show. The heroes of that movie thought they had killed almost all the piranhas, but they were wrong. The dead fish were just the babies, and the parents were somewhere in the deep blue waters, awaiting their turn at cannibalism.
Which is why there is Piranha 3DD, the official seque....