If you live anywhere near the center of Miami-Dade County and you find yourself overcome with the urge to go snorkeling, we suggest you head to the rock jetty at the southern tip of Miami Beach. (Metered parking available at South Pointe Park.) When the water is relatively calm, the north side of the jetty offers surprisingly good snorkeling, especially out toward its end, in deeper water. Lots of colorful reef fish, some barracuda, the occasional moray eel, even a shark now and then. But for the real thing -- namely, snorkeling on beautiful coral reefs -- we once again recommend Biscayne National Park. The big advantage: Only one snorkel boat per day, carrying a maximum of 49 people. No other commercial dive boats are permitted to operate within the park's watery boundaries. That sure beats John Pennekamp Coral Reef and State Park in Key Largo, which is so crowded you'll see more people than fish. The Biscayne National Park snorkel boat departs daily at 1:30 p.m. For $32.95 you'll get all the equipment you need (including wetsuit if desired), more than one hour in the water, and a delightful cruise to and from the reef. Reservations are recommended, especially on weekends.