After just 5 days in Lake Ontario and Sodus Bay, my father-law’s new boat came out dark brown. No product would remove the stains, until our local boat dealer suggested Slimy Grimy. I sprayed it on and within seconds the brown stains started to disappear. The product worked great with very little effort. It was the easiest hull cleaning I’ve done in 35 years. The only negative comment is that the spray trigger quickly became clogged and no longer worked (every other spray trigger I tried also became quickly clogged). Slimy Grimy is fantastic and I will use it for every hull clean from now on!