Drinking laws may be much more lenient on shore, for instance in the Caribbean. If a cruise line wants to be hard nosed, they can eject transgressors from the ship at the next port of call - at their own cost. The only hope of getting a drink on a cruise ship if you're an underage teen is getting some older sucker to buy it for you when no one's looking. Typically, the combination key/ID/charge cards each passenger is issued clearly indicate if the holder is under age. You may think anything goes in those lawless international waters, but truth is, the cruise lines maintain fairly strict policies governing the age at which you can drink booze, gamble and occupy a cabin alone.
