Many times I have trailered my boat after a day of fishing and there is some nasty brown "scum" on the hull. Always beforeI had to use rubbing compound to get it white again. The other day I was in Academy and bought some stuff called Starbrite Instant Hull Cleaner (9$). Well that is the first time I can remember buying something and the name said it all. I wiped that stuff on, and rinsed it off 2 minutes later and the brown stuff was gone. Also got rid of the stains that come out of the many different drains on the boat. I just had to go back and get the spotsI missed the first time. Great stuff, I highly recommend it. On thing I will do next time it wet the trailer first, because it left some spots in the galvanized surface.