Most marine paints are made to be immersed in salt water! They will scratch a lot more easily than automotive paint. Automotive paint on a boat, however, I think would be a no-no, cause the automotive paint isn't nearly as flexibile, and would crack off... Look in the Shoreway Marine Catalogue
(They are most likely on line, too.) They sell a teflon-based bottom paint that might interest your friend. Guaranteed to boost engine rpm and lower hull drag. No bottom growth, too.... I use it on snowblowers, up here, and sure enough, snow won't stick!
