We visited Culebrita in June and I understand the attraction. There are a lot of great options near St. Thomas. The cays between St. Thomas and St. John are great, but not a lot of white sand beaches. There are dive balls you can hit for free diving. Honeymoon Bay on St. John gives you some of the beach vibe; most of the North shore of St. John is National Park. Christmas Cove at Great St. James Island has is a preserve and has the Pizza Pi pizza boat.

Cheers, RickG