Virgin Islands National Park, which covers 63% of the island of St John, has converted me into a Caribbean traveler. With protection of the shorelines, reefs, and land provided by the national park's services, much of the island is still rustic and natural.
Trunk Bay(photo above), one of the most photogenic places on the island, is popular, though the beach is completely untouched and there isn't a resort in sight. The range of colors in water paired with the blinding white of the sand is unforgettable.
St John is highly recommended for those looking for more than just a resort on the beach in a Caribbean adventure.
More on St. John: http://travelshus.com/2012/06/01/the-natural-side-of-the-virgin-islands/