This movie was shot mainly aboard a real ocean liner. The Hamburg had recently been sold by its German owners to the Soviet Union. Before the Soviets took delivery of the liner, they rented it to the movie company. The liner was painted in the livery of a fictional shipping line, very similar to the livery used by the Soviet Morpasflot line, and renamed the "Britannic". Advertisements were run in British papers, soliciting extras who would take a lengthy cruise in the North Sea for free, but with the knowledge that the ship would actually seek out the worst possible weather, as the story demanded seas too rough for the lifeboats to be lowered, trapping the passengers on board.
This movie took its inspiration from an incident which occurred in 1972, when a man claimed he had planted a bomb on-board the Queen Elizabeth 2, and demanded a ransom. Cunard were prepared to pay the ransom, but the British Government decided instead to send in soldiers of the Special Boat Service, who parachuted into the North Atlantic one thousand miles from the U.K., and boarded the Queen Elizabeth 2 to search for the device. The threat turned out to be a hoax, and the F.B.I. later caught the culprit.
The project was originally to be directed by Bryan Forbes. After his departure, Don Taylor was hired, but departed four weeks before shooting was to begin. Richard Lester then came on-board. He re-wrote the script with Alan Plater. Writer and Producer Richard Alan Simmons was unhappy with the changes, and had his name taken off the movie, choosing to be credited as "Richard de Koker".
There were grave concerns when filming commenced without Richard Harris. Harris was in New York City, and the crew had to schedule filming around him, with the producers worried that he wasn't going to turn up at all.
The ship's steward Azad (Roshan Seth) is mentioned as being killed when a bomb goes off after he saves David McCleod (Adam Bridge) after he wanders into the area of the ship where the bomb squad is attempting to disarm the bomb by robot. Seen in one of the lobby cards for this movie, but not shown in the actual movie, his dead body is seen in the aftermath of the scene.
Director Richard Lester noted wryly that, after he had taken over the project (two earlier directors had come and gone before the start of filming), the shooting schedule was reduced by two weeks. He still brought this movie on time.
There are three references to the ill-fated R.M.S. Titanic in this movie. First, the fictional ocean liner's name is the "S S. Britannic", which was also the name of the Titanic's second sister ship, the H.M.H.S. Britannic, which also sank in 1916 after hitting a mine while serving as a hospital ship during World War I. Social Director Curtain (Roy Kinnear), also briefly references it twice in this movie. First, when he's preparing for the ship's costume party where he unintentionally references it by saying the party will be "a night to remember", which causes him to shudder when it reminds him of the famous 1955 book about the Titanic's sinking by Walter Lord, and its 1958 movie adaptation, and secondly, when the passengers are preparing to board the lifeboats, he and Barbara Bannister (Shirley Knight) are discussing the cold water and he says to her "There aren't any icebergs" to add a bit of cheerful advice to her. Also, at the beginning, the Britannic sets sail from Southampton, England, which was the first port from which the Titanic and her sister ship Britannic sailed at the beginning of their ill-fated voyages. The fictional Britannic's port of registry as seen painted on her stern in this movie is also Southampton. Interestingly, the ocean liner on which this movie was filmed, the T.S. Maxim Gorkiy, also struck ice in 1989 like the Titanic did, but her crew managed to prevent her from sinking.