The story is set at SeaWorld, a marine theme park where a pair of great white sharks infiltrate the complex via its lagoon. The eldest son of Martin Brody, Mike, now an engineer working at the park, notices strange occurrences and deduces that a shark might be responsible. Alongside his girlfriend, Kathryn "Kay" Morgan, who is a senior biologist at SeaWorld, they investigate, and their worst fears are confirmed when they discover evidence of a monstrous predator.

As the park prepares for a grand opening with underwater tunnels allowing visitors to observe marine life, chaos ensues when the sharks attack, putting both staff and guests in danger. Kay and Mike must work swiftly with the park's team to devise a plan to stop the giant shark before it can wreak further havoc. The tension escalates as they race against time to protect both the people and the marine animals in the park.