Back in 1990 when I was first certified as an MSF INSTRUCTOR (not a "RiderCoach") one of our Chief Instructors was a former submariner, and one of the other instructor candidates was also a former submariner. At the time, the latter was one of the guide/guards at the U.S.S. Nautilus in Connecticut.
The Chief was "George," the IC was "Spencer." The two of them would occasionally crack one quip or other that would make the other crack up. When the rest of the class would stare, the response was: "We could tell you, but then we'd have to kill you."
Another line George used a lot was "I spent ten years of my life in a submarine. I don't have to explain what I'm thinking." Or "I spent ten years of my life in a submarine. That explains EVERYTHING."