Sombrero Reef Marine Sanctuary- Marathon, Florida

Off the funky hamlet of Marathon, this spur-and-groove site —one of the largest coral colonies in the region— is home to angelfish, grouper and nurse sharks that seek the shelter of the 30-foot-deep reef system. Its signature lighthouse is a Florida Keys landmark.Local Dive Guide: Warm Water, Beginner Dives, Large Animals, Guide Needed, Year-Round