Hi, Thomas: " At seven o'clock, the morning of the 26th day of December, the S.S. Poseidon, 81000 tons, homeward bound for Lisbon after a month long Christmas cruise to African and South American ports, suddenly found herself in the midst of an unaccountable swell, 400 miles south-west of the Azores....."
FYI: There were 500 once class passengers aboard. Second and third class had been removed and replaced with cargo space making the Poseidon, in reality, a very big freighter. The stabilizers were partially damaged, and there was no balast. The dining room had windows which, after the capsizing, remained above the waterline allowing moonlight to filter into the room. Why they didn't escape through said windows goes unexplained. The literary Poseidon was capsised by a seabed landslide.
And imagine, once again, how the audience would have reacted had the movie ended as the book did with some of those who remained in the dining room emerging, still in their evening wear, from the bow.