Scuba diving and snorkeling are popular sports in the Florida Keys, and with good reason. Some of the best diving areas in the world are here. John Pennekamp Coral Reef State Park, created in 1963, was the first undersea park in the United States. Adjacent to the Florida Keys National Marine Sanctuary, the park encompasses almost 180 nautical square miles of coral reefs, seagrass beds, and mangrove swamps. The coral reefs are located between three and eight miles off-shore; tour them in a glass-bottom boat, or take a snorkeling or scuba tour.