When we went to Key West on the Magic in 2000, we booked the Fury Catamaran snorkel trip. It was great. I highly recommend it if you enjoy snorkeling. They take you about 7 miles out to sea to a reef which is designated as a national park. You anchor there and can snorkel for a few hours. There are complimentary beverages (beer/wine/soda), and the crew is great. The snorkeling was great, also.