I dont know any technical details about it, but there's a hell of a lot of blue hulls by us in SoF with very high salt concentration. The local french tend not to spend hours cleaning their boats, especially the small and often old ones, and despite this their hulls look very shiny and glossy and clean even after a quick rinse with fresh and sometimes salt water...

The bigger boats in the area probably go for a lift out and antifoul and scrub, but always look spotless.