I have used MaryKates On/Off Hull cleaner many times (the red and blue bottle not the gel). It does what is says! I keep my boat in the saltwater without bottom paint and it gets pretty nasty real quick. To me it cleans like magic, it will even dissolve barnacle calcium rings if you give it time. I'm using it as we speak, I left my boat in way longer than normal and have many barnacles attached, I pressure washed them off and now am wiping down with MK. Make sure you read and follow the directions because it is an acid and its fairly nasty to breathe or get on your skin. I always thoroughly wash and wax afterwards. It always leaves my hull looking good. My 2 cents!
