Key West is compact and walkable, so you can easily explore on your own. Have brunch outdoors at Blue Heaven. Rent a bike. Tour the Hemingway House for a glimpse of life here in the 1930s. Eat key lime pie (Kermit's is one of the top rated). Experience the shops and bars on Duval Street.
Organized shore excursions in Key West include a culinary tour, trolley tour, bike tour, helicopter tour, butterfly conservatory, and the aquarium.
Out on the water you can stand-up paddleboard, catamaran sail, snorkel, kayak, parasail, or snuba.