We spent the morning at the beach, having seen all the same shops in Charlotte Amalie, and did a Shore Excursions bus tour in the afternoon. It was a good value. The driver took us shopping in Marigot and we found some good bargains at a place he recommended. He was quite personable and told us a lot about the island.
Dawn Beach is where we swam -- we went to the cab stand off the pier and asked a driver what beach he recommended. Since we had a child, I think, he recommended a beach on the Dutch side where people are less likely to engage in "clothing optional" sunbathing (common on the French side, but illegal on the Dutch side). (We actually had prepared our daughter for the possibility not all swimmers would be fully suited up, and we're not prudish, but we appreciate his thoughtfulness nonetheless.) Dawn Beach is hard to reach in a bus because the streets are so narrow, so a lot of ship people don't go there. It's lovely and quiet, though there was food available and chairs and umbrellas were for rent at a reasonable rate.