I keep my boat out of the water so I don't have bottom paint. In the spring I spent the night at a friends dock and the water was a red tint during this time like you might see in the fall with leaves in the water. Since then I have some stubborn red stains on the hull below the water line. The only thing I've tried so far is generic boat wash and water but I would like to get rid of the stains. Anyone have any thoughts on what product may be good for this?