Passports

• A passport is a document issued by your government used specifically as identification when traveling abroad, though passports are typically accepted as proof of identity in other situations where such proof is required. On land, it is obvious when a passport will be needed, but at sea the situation is less clear. Most cruise ships require some form of photo identification, and suggest a passport for this purpose, regardless of whether or not one is actually required.
  
  

Closed Loop Trips

• Closed loop tried are defined as those cruises that depart and return from the same U.S. port. Also required is that passengers remain on the same cruise ship at all times. For these closed loop cruises, a passport is not required, though it is suggested. Boarding most cruise ships does require photo identification, however, so if a passport is not taken, an enhanced driver's license is often required. Getting off the ship in a foreign country, however, may require a passport, depending on the country in question.
  
  

Open Jaw Trips

• An open jaw cruise is one where you get on a cruise ship in one U.S. port and return to a different U.S. port. For these open jaw cruises, a passport is required, and photo identification such as an enhanced driver's license will not be sufficient. Keep in mind that if the ship makes any stops in a foreign country, you may also need a passport to enter.
  
  

Emergencies

• Something else to consider when deciding whether or not to take a passport on a cruise is emergencies that may come up while on the cruise. Cruises are known to occasionally have outbreaks that require disembarking, for instance. Bad weather could also cause you to have to get off the cruise unexpectedly. If you are forced to disembark in a foreign country and do not have a passport with you, getting back into the U.S. could be more difficult than it would be with a passport.