Julie, Novak, Fallon, and Deputy Taylor Roberts try to evacuate the lake, but their warnings are ignored, until the piranhas begin to fiercely attack the tourists.
Novak boards a jet-ski with a shotgun to help while Fallon drags people to shore, and Julie and Taylor try to get swimmers into the police boat.
He explains that it is a highly aggressive prehistoric species, long believed to be extinct, and that the piranhas have survived through cannibalism.
The species is able to vigorously devour its prey in seconds.
The others make it across safely, but the rope comes loose.