A closed-loop cruise is a type of cruise that departs and ends in the same U.S. port. This means that the cruise ship starts and ends in the United States, and the itinerary can include contiguous territories of the United States, such as Mexico, Canada, and several islands of the Caribbean. Closed-loop cruises are also known as round-trip cruises. To qualify as a closed-loop cruise, the cruise ship needs to meet specific criteria. One of the advantages of a closed-loop cruise is that U.S. citizens can take advantage of the convenience of not needing a passport for the trip. However, it is always advisable to check the documentation requirements for the destinations on the itinerary, as some may have different rules. For example, if you are a Lawful Permanent Resident (LPR) of the U.S., you may need your I-551, or Green Card, to re-enter the U.S.. If you are not a U.S. citizen or a U.S. LPR, you will need a passport regardless of whether you are on a closed-loop cruise or not.