Do you need a passport card for a cruise to Mexico?

Yes, you will need either a U.S. Passport card or booklet, which you will need to provide to the Cruise Line before the trip. Once aboard the vessel, the Cruise Line will issue you a card which will be swiped every time you leave or enter the vessel during the trip. You will probably not be asked to show a passport or passport card by Mexican authorities, but you must carry one with you at all times while you are in a foreign country.