You must be 18 to buy cards and to accept the winnings, but anyone can be holding the card and yell BINGO.
The cards must be purchased by someone over age 18
The winnings must be placed on the card of someone over age 18
Anyone can play and "win"
They usually hold one game per day. On port days they usually play just before or in between dinner seatings. On sea days they play in the morning or hold two games.