The rules regarding minor drinking on cruises in 2026 are strictly governed by the cruise line's policy and the ship's current location. For most U.S.-based lines like Royal Caribbean or Carnival, the minimum drinking age is 21, regardless of the ship's position in international waters. However, on cruises departing from Europe, South America, or Australia, the age is often 18. Some lines allow parents to sign a "parental consent waiver" for 18-to-20-year-olds to drink beer or wine only while in international waters. It is a peer-to-peer "legal warning" that "minor" status (typically under 18) strictly prohibits alcohol consumption on all major lines. Modern cruise ships use coded keycards that automatically block alcohol purchases for underage guests, and the staff is highly trained to spot "second-hand" drinking where an adult buys a drink for a minor. If caught, both the minor and the adult face consequences that can include being forced to disembark at the next port without a refund.