In 1981, the U.S. government began a wide-scale project designed to increase the number of habitats available to marine organisms. One of the program's major accomplishments has been the creation of nearby artificial reefs, which have attracted all kinds of tropical plants, fish, and animals. In addition, Biscayne National Park offers a protected marine environment just south of downtown.

Several dive shops around the city offer organized weekend outings, either to the reefs or to one of over a dozen old shipwrecks around Miami's shores. Check "Divers" in the Yellow Pages for rental equipment and for a full list of undersea tour operators.

Diver's Paradise of Key Biscayne, 4000 Crandon Blvd. (tel. 305/361-3483), offers two dive expeditions daily to the more than 30 wrecks and artificial reefs off the coast of Miami Beach and Key Biscayne. You can take a 3-day certification course for $399, which includes all the dives and gear. If you already have your C-card, a dive trip costs about $90 if you need equipment and only $35 if you bring your own gear. It's open Monday to Friday from 10am to 6pm and Saturday and Sunday from 8am to 6pm. Call ahead for times and locations of dives. For snorkeling, they will also set you up with equipment and maps on where to see the best underwater sights. Rental for mask, fins, and snorkel is $15.

South Beach Divers, 850 Washington Ave., Miami Beach (tel. 305/531-6110) will also be happy to tell you where to go under the sea and will provide you with rental equipment as well for $30, which includes the mask, fins, and snorkel. They also do dive trips to Key Largo three times a week and do dives off Miami on Sundays at $95 for a two-tank dive.