Float an inner tube in the center of the pool, then toss a bunch of ping-pong balls in. Have all the kids jump in, retrieve the balls, and try to toss them in the tube.
Fill The Bucket
Give your kids two buckets, one full of water and one empty, and a sponge. Get them to transfer the water from one bucket to the other using only the sponge.
Have everyone put on bathing suits and play tag. Whoever is "It" gets the water gun and tries to tag the other players with a squirt!
Minute to Win It - Ball Blast
Use ropes to create a circle on your lawn. Place balls of varying sizes and weights inside the rope circle. Give your child a hose and challenge them to push the balls out of the rope circle with the water in less than a minute.
Use the stream from a water hose as the stick for a high-stakes game of limbo.
Run a strong stream from a garden hose back and forth like a snake under your children's feet, allowing them to jump over it. Whoever's feet get drenched first loses!