A passenger ship is en route from New York to Greece. On New Year's Eve, the ship is taken over by a tidal wave and it turns upside down. All of the passengers die except ten lucky people.
The Poseidon Adventure is the mother of all disaster movies. The Poseidon is the largest ocean liner ever, bigger than the Queen Elizabeth and the Queen Mary combined. A ship full of passengers are celebrating New Year's Eve. Just after the New Year is rung in, the Captain spots a tidal wave. A huge tidal wave.
Soon, everybody else sees it, too. For almost all of the passengers and crew, it will be the last thing they ever see. The ship is capsized, turned completely upside-down, and only ten people have survived. Now those survivors must make their way from the capsized top of the ship up to the bottom before they drown as well.