I can see it now. You’re chugging along the channel at a leisurely 50mph in your boat when all of a sudden you get the urge to go under the water for a closer look at all that hides beneath the blue waters (or whatever color the water is your vacation in). If you’re on a normal boat, the obvious solution is to jump in. Conversely, if you’re in a submarine and want to get closer to what your see out of your little peep hole window, you’re out of...