Thank you both.
xort -- you're right about that. It's much more common than I thought. Just really freaked me out to see it on my own boat.
Another tidbit: Mr. WM said he saw this problem less often when the connection ports (at the boat) were the metal types with the screw-on caps -- as opposed to the plastic ones with the flip-up caps. Interesting. I have the latter - I think I'll invest in the former.