There is a product by "Captain John" that is carried by some West Marine stores. It is a store manager's decision on whether to carry it or not. There was some talk of putting it in the inventory on a company wide basis.
Anyway, we had a demo of it one weekend at West when I worked there. First, it is all natural with no caustic components. Two, you need to leave it on and not let it get below 50 degrees. Once applied, (roller, slabbed on by brush or sprayed) it needs to be covered with suran wrap or some other non-poruos film product. Even leave it on all night. Afterward simply take a plastic blade and scrape it off down to the gelcoat letting it simply fall into a paint tray or bucket. (The removed bottom paint is toxic!)
We took 5 coats of bottom paint off a wooden dingy with one application leaving only what paint there was embedded in the grain of the wood. About 80-90% of the wood was totally paint free. The stuff works!
Captain John's web site is:
http://www.captainjohnsboatbrite.com/Soy.htm
He's got a whole line of cleaner/polishing products and I use them for my car, boat, etc. Great products and a real nice guy to deal with!!!