I know about this... Its cool and all but you do the same thing pretty much as when you go to the dance club at night on carnival. They have contests where 2 people put water balloons under their chin and pass it on to the next person without breaking it.
They also have a Past Guest Party that they give free drinks. I've been to it and is fun. Past guests are invited by a card that they slip under your cabin door on the 2nd day of your cruise.. For a whole hour in this party , you drink all you like and to your hearts desires.. Pretty cool , you just have to be aware of it and read the brochures carefully!