I always bring a guitar with me when I'm on the boat.
I have a Taylor GS (7/8 scale) which is a good balance of sound for a small guitar. It's a laminate, so it does better than my solid guitars like my Martin 12 String (too big for a boat) or Taylor 314.
Admittedly, we only do weekends and a few weeks here and there. When we move onboard on a more 'full-time' basis (seasonally) I'll be bringing a carbon fiber guitar with me.
I prefer Elixer strings. With their polymer coating, they do well in a marine environment.