AMike Brody is working as a construction engineer at Seaworld, which has just installed an Undersea Kingdom exhibit, a set of four underwater tunnels that allow visitors to 'view the wonders of the deep without ever getting wet.' The complex has been built in SeaWorld's man-made lagoon, kept separate from the ocean by a steel gate. When the gate becomes compromised, a 10 foot Great White shark enters the park. Mike and his girlfriend, Dr Kathryn 'Kay' Morgan (Bess Armstrong), the senior biologist, try to capture the shark but it dies. Little do they know that the shark's 'mother', a 35-foot Great White, is also in the lagoon.