The plot centers on the SS "Poseidon", a 135,000-ton state-of-the-art luxury cruise ship on a cruise from Cape Town to Sydney as well as the stories and dramas of some of the 3,700 passengers and crew. A terrorist operation plans to sink the ship. Four terrorists take two bombs aboard to sink the ship. Sea Marshal Mike Rogo (Adam Baldwin) is assigned to the ship to search for any suspicious activity. Passenger and father, Richard Clarke (Steve Guttenberg), is having an affair with Shoshana, a crew member. His family is drifting away from him, and his wife Rachel (Alexa Hamilton) kicks him out of the family's stateroom. Dylan (Rory Copus), their 12-year-old son, witnesses this and is devastated. His older sister, Shelby (Amber Sainsbury), is in nursing school and falls in love with the ship's doctor Ballard (C. Thomas Howell).