Hemingway House, Key West Lighthouse, lunch on Duval Street, afternoon at the Butterfly Conservatory, sunset at Mallory Square.
Morning snorkeling or beach time at Fort Zachary Taylor, afternoon at Smathers Beach, evening sunset sail.
Full-day reef snorkeling or fishing charter, dinner at the Historic Seaport.
Full-day ferry trip to Fort Jefferson and the outer reef — book well ahead.
Drive north over the Seven Mile Bridge to Bahia Honda State Park, stopping at roadside seafood shacks along the way.