Travelers under the age of 21 must travel with a passenger who is at least 21 years old. At least one passenger in every cabin must be 16 years old or older; for cabins with solely guests under the age of 21, their reservation must be linked to that of a parent or legal guardian in another cabin.

You can go on a cruise at 18, but your ability to sail unaccompanied depends entirely on the cruise line and the ship's departure port. Most U.S.-based lines, such as Carnival, Royal Caribbean, and Celebrity Cruises, require at least one person in the stateroom to be 21 or older for sailings departing from North America. However, these same lines often lower the minimum age to 18 for cruises originating in Europe, Asia, South America, or Australia. Some lines are more flexible: Virgin Voyages (which is 18+ only), Disney Cruise Line, and Cunard generally allow 18-year-olds to book their own cabins and sail solo regardless of the port. It is also important to note that while you can sail at 18, the legal drinking age on most U.S. cruise lines remains 21, even in international waters, unless the ship is in a region where local laws allow 18-year-olds to drink. Always check the specific "Age Policy" of your chosen cruise line before booking, as being denied boarding due to age restrictions will not result in a refund.