Marathon is often considered the best place in the Florida Keys to snorkel, to deep-sea fish or to do anything that has to do with the water. At Starfish Snorkeling, the name of the game is exactly that, a place where the whole family can snorkel above the spectacular Sombrero Reef. The excursions typically last three hours and all equipment is included. If you have never snorkeled before, the instructors give a crash course and when your ready, the shallow Sombrero Reef is only between six and thirty-feet deep, so it is quite accessible even for the beginner.