5. Play "Duck-Duck-Goose" with a twist. Have everyone sit in a circle on the ground. Have one player touch each person on the head while saying "duck." However, in this version, the player touching heads also carries a cup of water. When he picks someone and says "goose," he pours the water on that player's head (this game is a lot of fun on a hot day but isn't for everyone. Some kids just like to sit on the sidelines and watch, which is just fine)!
6. Have water relays. Divide everyone up into two teams. The first two players run across the lawn carrying a paper cup full of water and dump it into a large bowl or small bucket. They then rush back and tap the next runner who now runs with a cup of water. The first team to fill their bowl/bucket wins!
7. Get a large bag of sand at your local gardening/landscaping store. Place it in a hard plastic kid pool. Let the kids pretend they're at the beach by adding water to build castles, make moats, and create bridges.
8. Construct an obstacle course with water features. Let the kids use items from around the house: chairs, ladders, hula hoops, a min-trampoline, ropes, tables, etc. Let them use squirt bottles, hoses, and sprinklers to add parts to the course where participants get wet.
9. Use spray bottles filled with water to squirt ping-pong balls across the lawn or driveway. Have races!
10. Give the kids lots of ice cubes and let them build sculptures using salt.