Biscayne National Park in Florida is 95% under the waters of Biscayne Bay. The park protects the unique marine zone between the Everglades and the Atlantic, including the northernmost Florida Keys that reach from Key Largo towards Miami.
These islands are accessible by boat - either a visitor's boat, or a tour run by the park's concessionaire. Most visitors take a glass-bottom boat tour or a snorkeling trip. The water is clearest and warmest in summer, and winter trips may not have as much visibility. The visitor center is near Homestead on the mainland, and it's easy to combine a trip to Biscayne National Park with a visit to the Everglades.
