A long time ago, way before I had a child, I heard a tip that I wrote in my classroom notebook should the need arise. Apparently baby powder sprinkled on a damp, sandy child dries and removes the sand instantly. I never had the chance to test it out until this Memorial Day weekend. We spent it at my parents' lake house. Although the lake is 15 feet above normal, we were able to find a small beach area to interrupt our boat ride with a little dip. We sat in the sand for awhile, and Miss Priss had sand everywhere in 2 seconds flat. As soon as we got back on the boat, I grabbed the powder and sprinkled her up. She went instantly from a sandy, wet, uncomfortable baby to dry and sand-free.
Awesome tip. Try it!