One of the old timers had an enormous steel hulled Chris Craft that he lightly maintained. He hired a company out of Buffalo to strip the bottom in the spring a few years ago. They came in, set up and blasted the paint off the bottom with dry ice chips. It was pretty wild to see, there was a big fog bank looking cloud, it did a pretty decent job though. He painted the bottom with some special military grade paint that was supposed to be the be all, end all for steel hulls.
Unfortunately, when they launched the boat a week or so later it partially sank in the lift well. They eventually hauled it away for scrap later that summer.