The capsized luxury liner S.S.
Poseidon is still afloat after six survivors have been rescued by the
French Coast Guard. Mike Turner, captain of the
tugboat Jenny, spots the rescue helicopter and finds the shipwreck. Accompanied by second mate Wilbur and passenger Celeste Whitman, Turner heads out to claim
salvage rights, as the
Jenny lost its cargo in the same
tsunami that capsized the
Poseidon. They are soon followed by Dr. Stefan Svevo and his crew, who claim to be
Greek Orthodox medics who received the ship's SOS. They board the vessel through the bottom hull opening by the French rescue team and come across the fires still raging in the engine room and the body of Linda Rogo. Eventually, there is an explosion deep inside
Poseidon. The group soon encounters more survivors, the ship's nurse, Gina Rowe and two passengers, Suzanne Constantine and war veteran Frank Mazzetti, who is searching for his missing daughter Theresa. Theresa is found, as are elevator operator Larry Simpson and Tex, a supposed billionaire who clings to a valuable bottle of wine. They also find the blind Harold Meredith and his wife Hannah, who were waiting to be rescued. Water continues to submerge decks, and more explosions occur. Turner's group find the purser's office, where Svevo decides that he and his men will search for other survivors, parting ways with the rest. Another explosion causes the safe in the purser's office to fall and open, revealing gold coins, diamonds and cash. Turner and Wilbur gather the coins. Unknown to Turner and the survivors, Suzanne is actually working with Svevo. She takes a list containing information about a cargo of crates from the office. Going off on her own, she gives Svevo the document but decides to rejoin Turner's group. Svevo orders Doyle, one of his men, to kill Suzanne. After being shot, a dying Suzanne strikes Doyle with an axe, killing him. While making their way up through the decks, Turner and the others find Suzanne's corpse and realize that a murderer is on board. Hannah dislocates her shoulder while helping Harold. Svevo and his men are found gathering a cargo of
plutonium. Svevo reveals that his real intention for boarding the
Poseidon was to retrieve his lost shipment of plutonium, adding that he cannot let Turner and his group go now. However, before anyone is killed, another explosion occurs, allowing Turner's group to escape. Turner, Frank, and Larry find guns. In the ensuing shoot-out, Frank and another of Svevo's men are killed. Water floods the room as Turner's group proceeds up to the next deck. An injured Hannah, unable to climb a ladder, falls into the rising water and drowns. While trying to rescue her, Turner loses all of his salvaged gold. Svevo and his one remaining gunman head back up to the ship's stern, where the rest of Svevo's team attempt to use a crane to raise the plutonium up to the hull, which is slowly sinking. In another section of the ship, Turner and the survivors exit the ship through an underwater side door. However, due to shortage of scuba tanks, Wilbur sacrifices himself by swimming underwater and disappearing. Turner and Celeste swim to the tugboat and move it closer to the
Poseidon as the remaining survivors swim towards it. Svevo's men see them and open fire. Tex, who in reality was not a wealthy passenger but a
sommelier from the
Poseidon's crew, holds onto his bottle as he is gunned down and perishes. The rest of Turner's group reaches the tugboat and sails away. Water continues to flood the
Poseidon, causing the boilers to finally explode, which detonates the plutonium cargo, blowing the ship in half and sinking it, killing Svevo and his men. En route, Turner accepts that his tugboat will be taken from him when they get to port, but Celeste reveals a diamond she salvaged from the
Poseidon. The two kiss, and the tugboat sails away into the sunset, bringing the total survivors of the disaster to ten. == Characters ==