If your Mexican cruise is a closed-loop cruise, which is a cruise the leaves and returns to the same U.S. port of call, you are not required to have a passport, passport card or a trusted traveler program card. Passengers of any closed-loop cruise between the U.S. and Mexico may present a certified copy of their birth certificate, naturalization certificate and photo identification. However, it is recommended that you do use a valid passport for travel in case a situation arises where you miss your boat and are required to then fly home from Mexico.
The U.S. Department of State issues passport books and cards to any qualifying U.S. citizen that completes an application and submits all of the required documentation to your local Passport Acceptance Facility. Passport books are the most common, and most expensive form of travel documentation available because they are the only form of travel documentation accepted in all countries at any entry point; land, sea and air. Passport books are similar to passport cards except that they are small, driver's license sized cards that contain the same information as your passport only they are much less expensive and fit right into your wallet. Passport cards are not permitted during any form of air travel but are usable for land and sea entry to any cruise port.
Enhanced Driver's Licenses are issued to residents of Michigan, New York, Vermont and Washington, as of 2011. EDL's are specialized driver's licenses that allow carriers to enter and exit the U.S. between the Caribbean Islands, Bermuda, Mexico and Canada by land or sea without a valid passport. If you are a resident of any of those states you may use your EDL as your travel documentation on your Mexican cruise. Trusted Traveler Program cards are issued to any U.S. citizen that crosses either the Canadian or Mexican border on a regular basis for work and/or personal reasons. With your Trusted Traveler program card (called the Nexus or Sentri cards) you can cross the Mexican and U.S. borders by land or sea without needing your passport or passport card.