If the water ain't changin' often or if there's ambient pollutants......and I gotta say Tacoma has long been famous for ambient pollutants. If you're out moving in the water going somewhere..I haven't been anywhere but I have read about going somewhere...then the pollution quotient of the soft paint is greatly reduced over scrubbing in which a large amount may be scrubbed off in one location. In motating thru the water..or so I've heard..it happens a lot more slowly.