I took Phil's suggestion last year and installed the transducer drivers for speakers. I ran installed them in the lazarette on the back side of where I would have otherwise cut out speaker holes. I get sound that's nearly as good as the custom sealed enclosure 6.5" coaxial speakers installed in the cabin. They required absolutely no drilling or cutting, you cannot kick them in, they will not rot from the UV or weather (at least no faster than the rest of the boat), and they were cheap ($20ea!), and if you don't like them, peel them off!
It took some experimenting to figure out where I wanted to place them to get the best sound (you can hold them against the surface and get a good idea how it will sound before mounting them), but ultimately I chose to install them right where I planned to put regular speakers (I had even purchased regular speakers for the cockpit and spent $100 having custom mounting brackets made to give a good waterproof seal before finding out about these, but hadn't yet installed them due to doubt about cutting such large holes in the boat for something that wouldn't last 10+ years), but once I realized these sounded as good as I was hoping for from the regular speakers, and any minor improvement wouldn't be even remotely worth the holes required for anything else, I returned the traditional speakers and have been loving my setup ever since.
With this knowledge, anyone who cuts or even drills a hole in their cockpit to install speakers (or recommends anyone else do so) without at least first trying these transducer drivers is just plain dumb.