1 beach towel for every 2 people. Water Balloons (large balloons tend to be more fun!). A Volleyball net.
Like Volleyball the object is to score the most points and get the other team wet at the same time.
Form 2 teams. Have each team stand on either side of the volleyball net. Have each team divide into pairs. Each pair should have one towel and each person should grab 2 corners of the towel so that it is spread out between the pair.
A water balloon is placed on the towel of one of the pairs. The pair must then work together to lift their towel so that the balloon is propelled into the air, across the net to the other team. One of the pairs on the other team must then try to catch the balloon with their towel and return it the same way.
As in regular volleyball, a team scores a point when the balloon hits the ground on the other side of the net.