A young woman's horribly mangled body is washed ashore on the beach at a small New England town. The new police chief, Martin Brody, is told by the pathologist that a shark is the most likely cause. Soon, another shark attack follows, and a shark-hunting frenzy erupts.A small tiger shark is caught. Matt Hooper, a marine biologist with a special interest in sharks, declaresthat they've killed the wrong shark.
However, the local mayor, Larry Vaughn, insists that, for the sake of the local economy, the town's beach stays open for the 4th July holiday crowds. Inevitably, a swimmer is horribly killed by a huge shark right in front of the holiday crowds.
Martin and Matt, are joined by Quint, a gnarledwise old fisherman, in a hunt for the killer shark.