To help the audience quickly grasp which sub's interior they were seeing as the movie jumped from scene to scene and sub to sub, the filmmakers created a subtle lighting scheme: red for Dallas, blue for Red October, and green for the other Russian sub.
While preparing for his role in the film, Scott GlennScott Glenn met the captain of the U.S.S. Salt Lake City. Glenn then composited the captain into Bart Mancuso.
Jack Ryan takes a teddy bear home with him at the end of the film. McClane has one at the start of Die Hard(it's the same bear).
The underwater model of the Red October has never been in the water. This effect was achieved using smoke on the 'underwater' set and a few digital touch-ups. The sub was hung by 12 wires from an overhead grid which gave the ability to tilt and turn the model as needed.