If the ship begins and ends its voyage at the same domestic port, passengers can board by showing an official government birth certificate and — for anyone 16 or older — a government-issued photo ID. 

Of course, there are some exceptions: Barbados, Guadeloupe, Haiti, Martinique, St. Barts, St. Martin, and Trinidad and Tobago all require cruise passengers to have a valid passport in order to enter their countries. However, you can sail on a cruise that calls on these islands, as long as you stay on the ship at these ports.

One point to remember: Just because you can cruise without a passport doesn’t mean you should. If you were to miss the ship, not having a passport would make reentry into the U.S. a nightmare.  The laws governing international travel can be complex. Rules may vary based on the port of origin, the itinerary, and the home country of the passenger. If you have any questions about what documents are considered acceptable identification, the best thing to do is contact your cruise line.