Dive 90 feet under the sea to one of St. Thomas's most beautiful reefs without getting wet. Atlantis Adventures (Havensight Mall, Bldg. VI, Charlotte Amalie. 340/776-5650. www.atlantisadventures.com) has a 46-passenger submarine that takes you to a watery world teeming with brightly colored fish, vibrant sea fans, and the occasional shark. A guide narrates the one-hour underwater journey, while a diver makes a mid-tour appearance for a fish-feeding show. The cost is $89. No children shorter than 36 inches are allowed.