I just put this to the test on my 23. I left the boat on a mooring for 5 weeks
no problems up until somewhere b/w week 4 and 5. There are 3 areas where I lost sheets of imron paint . . . about a 12" section and 2 6" sections. I was going to bottom paint the boat anyway for next year . . . just in case you were wondering what happens when you leave imron in the water below the waterline : )