Times have been hard since a swarm of bloodthirsty fish terrorised the area around Lake Victoria. In the year since, tourism has dried up and, in an effort to drum up trade, waterpark owner Chet (David Koechner) has turned his attraction into an adult playground complete with strippers as lifeguards, much to the disgust of his stepdaughter Maddy (Danielle Panabaker).
The ploy seems to be going well, until reports of mysterious deaths prompt rumours that the prehistoric piranhas are back. After investigations from boffin Mr Goodman (Christopher Lloyd), it becomes clear that the toothy predators are using underwater rivers and sewage pipes to travel between the lakes. If they find their way through the system and into the water park, it will soon be feeding time.
The creators of this over-the-top sequel to 2010's already ridiculous Piranha 3D know exactly what they have unleashed on the movie-going public. They have fun in lampooning myriad horror clichés, and never go so far as to create any serious scares among the often amusing blood-splattering. The casting of David Hasselhoff is a coup, and he revels in sending himself up in a film that casts the plot adrift and returns to a tried-and-tested formula of wanton flesh-flashing and corny comedy.