Leinster Bay and Waterlemon Cay lie inside the boundaries of the Virgin Islands National Park – which isn't surprising, since about 60 percent of St. John lies inside the park's boundaries. Other favorite spots include the island's number-one snorkel destination, Trunk Bay, with its famed underwater nature trail. Trunk, of course, shouts out from every visitor map and package-tour brochure, but early in the morning before the crowds begin to arrive, it is a magical place. Stingrays forage in the sand, turtles in the grass, and in the summer, an explosion of baitfish attracts schools of huge tarpon. Once the maddening crowds arrive, head off the beaten path to Haulover Bay, on the northeast coast, to visit its healthy corals. Or for a combo day of great beach and great snorkeling, head to Hawksnest Beach, with its beautiful backdrops of elkhorn forest populated by schools of grunts and blue tangs. For a professional underwater photographer like Simonsen, snorkeling on a day off may seem like a busman's holiday, but when you live on St. John, it's a magic bus.