Divide everyone into two teams and line up the swimmers in the water on either side of the pool. Dump a basketful of numbered Ping-Pong balls in the center of the pool while the players watch. At the sound of a whistle, both teams scramble to collect as many balls as possible and carry them back to a bucket on their side of the pool. No team member may collect more than one ball at a time. When all the balls have been collected, the numbers on the balls are added up, and the team with the highest score wins.