Well, my boat was in the water for about 4 months. I brought it home today and did the preliminary clean-up. Easy with a genuine car wash liquid, a soft brush on the end of my boatpole and a gentle hosing. Everything cleaned up, including the $800 bottom paint we got when we were in the salt water in Everett. The boat obviously lists to port, because of weight distrbution and, I guess, tying up on that side. So the scum line, or crud, if you prefer, wouldnt come off on the port. I went over it again with a sponge-nothing. Then, after I checked to see that Dotty wasn't watching, I tried the power washer, first with a fan, then with a pinpoint. Nada! I told Dotty, she looked up from her book in her recliner and said "Try the Collonite Fiberglass Cleaner # 920." Back to her book. Well to make along story a little less long, it works like a charm. I of course didn't bother with the directions, just applied it with a wet sponge, waited 2 minutes, brushed and rinsed it off. Shazam!