I marveled at the significant number of boldly colored "go-fast" yachts in St. Tropez. Black, burgundy, lipstick red, royal blue hullls, etc. I witnessed most of these being rinsed off daily by the yacht dealers and by local services. Of course they always looked stunning and there was never a water spot to be seen. Hmmm...how is it that I can't rinse off a thing on my WHITE boat, without having visible water spots.
Saw the answer today, in the second picture below. The rinser-offers always use a temporary water filter to remove the minerals and other impurities from the water!