- you are flying into or out of the United States of America
- you traveling into or out of the U.S. by land border-crossings or ports-of-entry by sea from Canada, Mexico, the Caribbean, and Bermuda
However, there is an Exemption if you are cruising from a U.S. Port and returning to the same U.S. Port. Other paperwork can be used instead.
It is called the
Closed loop Cruise exemption – (from Customs and Border Protection)
U.S. citizens who board a cruise ship at a port within the United States, travel only within the Western Hemisphere, and return to the same U.S. port on the same ship (referred to as a “closed loop” cruise), may present a government issued photo identification, along with proof of citizenship (an original or copy of his or her birth certificate, a Consular report of Birth Abroad, or a Certificate of Naturalization).
You may still be required to present a passport to enter the countries your cruise ship is visiting. Check with your cruise line to ensure you have the appropriate documents.
If you utilize this exemption and for some reason (illness, emergency, the ship sails without you) find yourself having to return to the U.S. a different way, you will have great difficulties. I recommend that you always have a Valid Passport when traveling.