If you happen to live in the NW, visit Gig Harbor Audio.
For $1,000 they offer a pair of bookshelf speakers that
beat anything I have heard suitable for bookshelf.
They actually have a pair mounted in a bookshelf.
Not sure if you have considered the marine environment's effect
on speakers? There are brands designed for tougher conditions
as you will be experiencing.
Keep us posted on your outcome!