A splashtastic twist on an old party classic: diving board charades!
Divide your group into teams and create a list of characters/concepts/ideas to act out (adjust your answers to suit the age of your group). The team on call must sit along the edge of the pool near the deep end. Set a timer for 3 minutes. Have the actor stand on the diving board (a perfect stage) and slowly move forward towards the edge as he or she acts out the clue. If the team correctly guesses, the actor may gracefully (or not so gracefully) dive into the water. But if the team fails to guess the clue, the actor must cannonball to splash his or her team! When the actor emerges, he or she must swim to the edge and rejoin the team before the next actor may begin.
One of the best parts about this game is the actors themselves decide when to give up on the clue. You may get the cautious actor, painstakingly acting it out. Or, you can get the cannonball-happy splasher. Ever group is different!