Passenger ferry
Key West Express states that the voyage is approximately 3.5 hours port to port. The crossing replaces the long highway with open water and gives the island a different kind of arrival: Key West appears as a destination reached across the sea rather than at the end of a road. Boarding begins 60 minutes before departure and check-in is required at least 45 minutes before departure. Verify the schedule, fare, baggage allowance, parking, and cancellation terms for your travel date.
Private vessel
Private boaters must plan around marine forecasts, fuel range, dockage, and local harbor conditions. U.S. Customs and Border Protection says operators arriving from a foreign port or place must report arrival. CBP lists Key West among Florida reporting locations and provides the ROAM process for eligible travelers.
Cruise ship
A cruise call gives a limited shore window. It is best evaluated as an excursion day with a firm return deadline, not as a substitute for reaching Key West for a hotel stay.