When flesh-eating piranhas are accidently released into a summer resort's rivers, the guests become their next meal.

Each year the population of sleepy Lake Victoria, Arizona explodes from 5,000 to 50,000 residents for the annual Spring Break celebration. But then, an earthquake opens an underwater chasm, releasing an enormous swarm of ancient Piranha that have been dormant for thousands of years, now with a taste for human flesh. This year, there's something more to worry about than the usual hangovers and complaints from locals, a new type of terror is about to be cut loose on Lake Victoria.

A scuba diving instructor, her biochemist boyfriend, and her police chief ex-husband try to link a series of bizarre deaths to a mutant strain of piranha fish whose lair is a sunken freighter ship off a Caribbean island resort.