A few lines (including Royal Caribbean, Celebrity, Princess and Norwegian) allow 18- to 20-year-olds to drink alcohol in international waters if their parent or adult guardian signs a waiver form.

To legally consume or purchase alcohol on a cruise at age 18, the rules depend entirely on the ship's itinerary and departure port. For cruises departing from and returning to the United States (including the Caribbean, Alaska, and Hawaii), the minimum drinking age is strictly 21, and there are no exceptions. However, for cruises in Europe, Australia, South America, and parts of Asia, the minimum drinking age is usually 18. Some cruise lines, such as Norwegian, Royal Caribbean, and MSC, allow 18-to-20-year-olds to consume beer and wine even on certain U.S.-based international itineraries if a parent or legal guardian is present and signs a "Young Adult Alcoholic Beverage Waiver" at the Guest Services desk once the ship reaches international waters (usually 3 to 12 miles from shore). It is important to note that this waiver typically does not include hard liquor or cocktails. In 2026, cruise lines are increasingly strict about these policies; if an underage passenger is caught drinking without a waiver, or if an adult provides alcohol to a minor, both parties can be fined or even forcibly disembarked from the ship at the next port without a refund.