In the quaint New England coastal town of Amity Island, a young woman goes for a late-night swim during a beach party. Her joy is abruptly cut short when an unseen force attacks her, pulling her beneath the waves. By morning, fragments of her remains wash ashore. After the medical examiner identifies the cause as a shark attack, Police Chief Martin Brody takes action to close the beaches. However, Mayor Larry Vaughn persuades him to reconsider, citing concerns about the town's summer tourism and economic vitality. Under pressure, the medical examiner revises his findings, suggesting the incident was a boating accident instead. Reluctantly, Brody accepts this conclusion—until tragedy strikes again. A young boy, Alex Kintner, is killed in plain sight on a crowded beach.

To address the growing danger, a $3,000 reward is announced for capturing the shark, sparking a chaotic surge of amateur hunters. Among them, a gruff and eccentric local shark hunter named Quint offers his professional services, demanding $10,000 for the job. Meanwhile, marine biologist Matt Hooper examines the remains of the original victim and confirms that she was killed by an unusually large shark, deepening the urgency to confront the menace.