A seismic tremor in a small resort town causes the lake's floor to crack open, releasing prehistoric piranhas into the water. Sheriff Julie Forester and her team are immediately concerned about the potential danger these voracious fish pose to tourists, especially during the bustling Spring Break season. Despite their efforts to warn the public, young adults flock to the lake, drawn by promises of sun and fun. Julie's son, Jake, becomes entangled with a group of partygoers, complicating her mission to ensure safety. Unbeknownst to the party crowd, the lakeside revelry sets the stage for a terrifying bloodbath.

Chaos erupts as the ancient piranhas claim their first victims, turning the once picturesque lake into a scene of carnage. The Sheriff's attempts to control the situation grow increasingly desperate, as the sheer number and ferocity of the piranhas prove to be overwhelming. Marine experts and locals must band together, devising strategies to contain the threat and rescue the surviving tourists. As the piranhas wreak havoc, the characters face the challenge of outwitting the relentless predators amidst a backdrop of fear and uncertainty.