The ship used by the filmmakers was the SS Ile de France, the famous French liner that cruised the Atlantic from 1926-59. She was leased for $4,000 a day. After shooting completed, she was re-floated (having been partially sunk for the film) and towed to the scrap yard. She has a more heroic place in history, however. It was she that played a major role in the rescue of the passengers from the Italian liner Andrea Doria in 1956, after the latter ship collided with the Swedish ship Stockholm and sank off the coast of Nantucket, Massachusetts. She was the first ship to arrive at the scene of the collision and immediately began taking aboard the Andrea Doria's passengers.
According to maritime historian William J. Miller, the famed French Line was so horrified that its former flagship would be used in such a way that it demanded that the Ile de France's name be removed from her bow and that in no way would any references be made to them.
Edmond O'Brien took issue with the safety precautions during filming, and left the production in protest. When he returned, he discovered that his part had been greatly reduced and he was no longer required on set.
For the scene in which the dining room is seen flooding, with water rushing in through the portholes, fire boats were positioned alongside the ship. They fired water at the portholes into the dining room, which was still well above sea level.