Cruz Bay Watersports (tel. 340/776-6234), is a PADI and NAUI five-star diving center. Certifications can be arranged through a dive master for $350. Beginner scuba lessons start at $95. Two-tank reef dives with all dive gear cost $85; wreck dives, night dives, and dive packages are available. In addition, snorkel tours are offered daily.

Divers can ask about scuba packages at Low Key Watersports, Wharfside Village (tel. 800/835-7718 or 340/693-8999). All wreck dives offered are two-tank/two-location dives. One-tank dives cost $58 per person, with night dives going for $70. Snorkel tours are also available at $35 to $120 per person. Parasailing costs $60 per person. The center also rents watersports gear, including masks, fins, snorkels, and dive skins, and arranges day sailing trips, kayaking tours, and deep-sea fishing.

Snorkeling gear can be rented from the Cinnamon Bay Watersports Center (tel. 340/776-6330) for $5, plus a $25 deposit. Two of the best snorkeling spots around St. John are Leinster Bay and Haulover Bay. Usually uncrowded Leinster Bay offers some of the best snorkeling in the U.S. Virgins. The water is calm, clear, and filled with brilliantly hued tropical fish. Haulover Bay is a favorite among locals. It's often deserted, and the waters often clearer than in other spots around St. John. The ledges, walls, and nooks here are set very close together, making the bay a lot of fun for anyone with a little bit of experience.