The film was "scripted by cult director Jack Hill and David P. Lewis, but attributed to John Robins for Canadian movie business reasons" according to 'The Spinning Image' website.
The number of survivors from the luxury ocean cruise liner was nine. On the film's main movie poster though only six survivors are depicted on the lifeboat.
The footage showing the movement of the Death Ship was the result of filming from a small boat moving around the Death Ship. The crew shot for about an hour before the 'Death Ship' broke down. The rest of the required shots were achieved by faking movement, as the broken vessel was anchored and stationary.
At the beginning, when the Death Ship is steaming full ahead at the cruiser, it is twilight. However, in the shots of the cruise ship it is clearly nighttime.
At the 51-minute mark, there is a sequence in which the character played by George Kennedy emerges in a dark uniform atop the ship while the character played by Richard Crenna looks from below. During three separate long shots of Kennedy, a crew member and camera are plainly visible to the left of the screen.
When the group first comes up upon the ship after it sunk the cruise ship, you see one of the windows open up, you can clearly see a person's arm when he opens the window, it is supposed to be opened by a ghost, which it clearly isn't.