The sleepy coastal village of Amity Island is preparing for the arrival of thousands of tourists for its massive Fourth of July celebration. However, there's a hitch in these plans. A shark attack has left a young woman dead, and the vicious creature could still be out there. The sheriff is keen to keep everyone out of the water, but the mayor can only see dollar signs and orders the festivities to proceed as planned, which leads to disaster. When one shark attack too many finally convinces the mayor to keep the water vacated, the sheriff sets off with a marine biologist and a grizzled fisherman with a mysterious past to pursue the beast in open water, learning about himself in the process.