For round-trip sailings (cruises that depart from and return to the same U.S. port), U.S. citizens may sail with either a valid passport, or proof of citizenship and a valid government-issued photo I.D. (driver’s license with a photo), or any other WHTI compliant document.
We highly recommend that all guests carry a passport. Your passport must be valid for at least six months beyond the completion date of your travel. A passport will enable you to fly from the U.S. to a foreign port in the event you miss your scheduled embarkation or to fly back to the U.S. if you need to disembark the ship mid-cruise due to an emergency.