Thirty-five years ago I bought a Japanese-made acoustic guitar in Hong Kong
. It was a "Morris" brand, came with a hard case, and cost $35. It was a copy of the famous Martin D-28 dreadnought. Good bargain.
I carted this guitar all over the world. It has lived on my sailboat for the past 19 years, 11 of them in the Caribbean
. Without the case. Kept having one problem...the bridge glue kept giving way, so I opted for a sailor's solution and put two short 1/2" s/s bolts through the bridge, along with a liberal coating of glue, a couple of big washers, and nuts.
This didn't change the tone one bit. And, the bridge is still intact. The guitar still sounds great. In fact, it has a better bass than does the real D-28 (which I now own and keep ashore, naturally).
Moral: don't be concerned about keeping an acoustic guitar on board. They can take it. Just need to change the strings more often than you would ashore.
BTW, I've heard those "boat guitars". IMO, they can't hold a candle to a real guitar :-)