Best smaller than bookshelf speakers?

try Gallo. www.roundsound.com

yes

I agree ,, the Gallo speakers ar just what you need ....

Why not call a custom installer in your area to find out what in-wall or in-ceiling speakers they carry and possibly install in your boat? Most in-wall/ceiling speakers made today are of the weather resistant variety and can sound pretty good if you keep the application in mind. Are you going to be critically evaluating music on your boat, or do you just want to create some ambiance with the ability to rock & roll every once in a while? Speakercraft, Sonance and Paradigm all have good models to choose from.
Good luck and enjoy!

B&W leisure monitors, they have built-in brackets and they are weatherproof.

What is you budget. Cambridge Soundworks also makes small satellites like Bose. Not expensive and better than Bose.

If you haven't heard the Acoustic Energy Aego2, check them out they will blow your mind. They are even self powered so you can connect directly to your source. They are the same size as the little Bose with a smallish subwoofer like the Bose but that is where the similarity ends. I had the Bose in a small office system 4 years ago so I know what they sound like. Trust me on this one, the Aego2s MURDER the Bose! They were reviewed VERY favorably my Michael Fremer in Stereophile and were on the cover of the mag about 6 months ago if you want to see them.

I heard them in two different set-ups and simply could NOT believe the sound they produced. Not to be snobby, but I have a main system worth over $100,000 retail and these tremendous little speakers make you think twice about price-points of different gear. The soundstage, imaging and timbre were simply amazing at 4 times the price let alone their paltry $599.00 retail price. I cannot recommend these speakers highly enough.