Yes, a 12-year-old generally needs a valid U.S. passport book to travel to the Bahamas, especially if traveling by air. For air travel, a passport book is mandatory for all ages, including infants. However, there is a specific exception for "closed-loop" cruises—those that begin and end at the same U.S. port. On these specific cruises, U.S. citizens under the age of 16 may be permitted to travel with just an original birth certificate (or a certified copy) instead of a passport. Despite this exception, travel experts and the State Department strongly recommend a passport for all travelers, as it is required for emergency air travel back to the U.S. if the child misses the ship or has a medical emergency while in the Bahamas.