Do I need a passport to go on a cruise? Here is the correct answer directly from U.S. Customs and Border Protection.

Most cruises beginning and ending in the same location are considered "closed-loop," meaning they begin and end at the same port in the United States and travel within the Western Hemisphere. For instance, if you board a cruise ship at Fort Lauderdale, Florida, and after visiting at least one foreign port of call, such as Bermuda, or Cancun, and return to Fort Lauderdale, you have taken a closed loop cruise. However, if you board a cruise ship in San Diego, California, sail through the Panama Canal (stopping at a foreign port during the cruise), and end the cruise in Miami, Florida, you have not taken a closed loop cruise. The Western Hemisphere Travel Initiative (WHTI) requires you to travel with a valid passport (including infants).

U.S. citizens on closed-loop cruises will be able to enter or depart the country with proof of citizenship, such as an Enhanced Driver's License (EDL), a government-issued birth certificate (issued by the Vital Records Department in the state where he or she was born) or passport, and if 16 or older, a government issued driver's license, picture ID, denoting photo, name, and date of birth. The Enhanced Driver's License (EDL) allows you to re-enter the United States from Canada, Mexico, and the Caribbean. The EDL is only accepted at land and sea border crossings, not for air travel. An U.S. citizen under the age of 16 will be able to present either an original, notarized or certified copy of his or her birth certificate, a Consular Report of Birth Abroad issued by Department of State, (DOS) and/or Certificate of Naturalization issued by U.S. Citizenship and Immigration Services (USCIS).

U.S. Customs and Border Protection (CBP) only provides the documentation required to enter the United States. However, it is possible that one or more of the destination countries on your itinerary may require a passport to enter. In those instances, the cruise lines would require passengers to have a valid passport to board even if it is not a U.S. requirement. You should check with your cruise ship, travel agent, and destination country to confirm the requirements to enter the foreign countries you will visit.  DOS recommends that everyone taking a cruise from the United States have a passport book in case of emergency, such as an unexpected medical air evacuation or the ship docking at an alternate port. 

Baptismal papers and hospital certificates of birth are not acceptable. Voter registration cards or Social Security are not considered proof of citizenship. If the child is a newborn and the actual birth certificate has not arrived from the Vital Records Department, we will accept a hospital issued birth certificate. The United States does not require you to have a passport. (A Consular report of Birth Abroad issued by the Department of State or a Certificate of Naturalization is also acceptable.)

If you are a Lawful Permanent Resident (LPR) of the United States the U.S. government does not require you to have a passport for any travel, including air, land, or sea travel, however, you are even more likely to be required by your destination country to have one. A Caribbean Island that does not require a U.S. Citizen to have a passport may require a U.S. LPR to have one, and a visa as well. An LPR is required to present an I-551 (Green Card) for reentry into the United States.

If you are not a U.S. citizen or an LPR, you will need a passport and/or the appropriate documentation based on the status you are seeking in the United States for any type of cruise, closed loop or not. If you are traveling under the Visa Waiver Program (VWP), your I-94W (immigration stamp) that you were issued when you first entered the United States can be used for reentering the United States at the end of your cruise - as long as the cruise ends before your 90 day admission period has expired and you did not travel beyond adjacent islands or contiguous territory, and you were not outside the United States for more than 30 days. If the cruise takes you beyond that 90-day admission period, you will have to apply for a new admission, and you will have to convince the CBP Officer that you were not taking the cruise to circumvent the 90-day limit for VWP travelers. To apply for ESTA, visit the ESTA website: https://esta.cbp.dhs.gov/esta/.

Closed-Loop Cruises Exceptions:

Generally, if a cruise starts and ends in the same US port, it's considered a closed-loop cruise, and a passport isn't typically required for the cruise itself.  However, some Caribbean islands, like Barbados, Guadeloupe, Haiti, Martinique, St. Barts, and Trinidad & Tobago, have their own immigration policies and may require a passport for entry, even if you're on a closed-loop cruise or plan to embark or disembark there.  Labadee, Royal Caribbean's private island in Haiti, is an exception and does not require a passport.    Always check with the cruise line you are traveling with to confirm these requirements.