A swimming/water game for hot days which combines water balloons and singing.
Swimming pool Water balloons
Have the kids wait in a designated area in the water and toss water balloons for them to catch. After throwing a couple, tell them that they don't get anymore unless they sing a song (try nursery rhymes). Every time they sing a song, throw in a few more balloons and try a different song or make them say something like: "I love swimming!" or "Happy Birthday!". Continue this until you are out of balloons.