Character mistake: Characters refer to the Dallas and the Red October as "ships," but anyone stationed aboard a submarine would know to call it a "boat."
Character mistake: As the helicopter crewman sees the Dallas surfacing, he says something along the lines of, "Sub at three o'clock". The next shot is from inside the helicopter and shows the sub and a part of the starboard landing gear retracting pod. This shot puts the Dallas closer to one o'clock. (01:24:00)
Chosen answer: They use it to wipe the grease pencil markings off the screens.
We called it "the Duty Roll."