What you need: a volleyball net, a bucket full of water balloons, and one towel for each pair of participants.
How to Play: Partners each hold the narrow end of the towel so that they have a cradle to catch the balloon and then pull the blanket quickly to launch the balloon back up in the air to the other team’s side.
The point is to score by exploding the water balloon on the other team’s side. if the balloon hits the ground but doesn’t break, it still counts as a point… it shouldn’t have hit the ground. Exploding a balloon in someone’s towel gets an extra point.
All the other rules are the same as regular volleyball… you can modify them so that they have to pass to at least one teammate before going over the net to make it more interesting.