When watching the start of the S/H today there was an ad. for luxury cruises on the Emerald Azzura that reminded me Daughter and SiL did the cruise a few months ago in a stern suite . Every morning the stern railing would be covered in diesel exhaust grime and ,i think he said ,the starboard side of the hull would be black . Whenever they pulled into port workers would get off the boat with large rollers and tubs full of white paint and paint over the diesel stains . Easy solution.