Using quality putty, on-deck areas that are often wet or exposed to the marine environment are formulated to withstand moisture. Most glazing putty is mixed with clay because it is less expensive. Clay and poly resin attract moisture have unreliable staying power which is prone to issues. Piranha putty by 3M is designed as a filler or a skim coat for light application and imperfections. This product is easy to sand is non-staining and comes in a 21oz tube.