have a cheap six stign for the boat but I hated playing it and teh humidity wreked havoc on it and it needed constant tuning. I won't bring my good guitars on boars so I finally settled on a Martin LXM.
The Martin LXM is made of a composite that looks a lot like Formica and the neck is made of a massive lamination schedule that basically makes it nearly inert to moisture variation and tuning issues. It sounds amazing for the size and sounds oodles better than my Big Baby Taylor did but never or very rarely needs tuning. It plays well, but it's no Santa Cruz, and also has decent low end for a mid sized guitar. It also takes up less boat space an an OM or Dreadnaught does..
I'm a big fan of the Martin LXM for the boat.. Neck & Body (photos courtesy of Elderly Brothes Music - one of the best sources of fine acoustic instruments in existance)