The dang stuff just gets all over everything, and if you don't get it off, you'll pay the price of new turning to old in a big hurry. If you've never watched a professional captain or crew washing down a large yacht, you'll see that they all follow the same basic procedure that I'll explain in a moment. Oh, I know that this might seem like a no-brainer, but believe me how good a job you do can make a huge difference on how good your boat looks a couple years from now. First, let me tell you about a few more bad things that salt can do to your boat. Yep, it can.
Salt actually has several negative effects on anything it comes in contact with.
First, you already know that it is corrosive to metals. What you're less likely aware of is that it is also corrosive to boat finishes of all kinds, including gel coat. That's why the finish on your hull sides, which don't get much sun, also deteriorates as though it were getting the full dose of ultra violet. But when salt dries into crystals, it's also abrasive, just like sand. Moreover, salt is hydroscopic.