Wet relay game!
Divide the campers into two teams and have them line up behind a starting line. Each team gets a small empty bucket and a large sponge. At the finish line, place two larger buckets filled with water. Tell the campers that on the word go, the first person in line must run to his/her team's water bucket, dunk the sponge in, run back with it and squeeze all the water from the sponge into the team's empty bucket. They then pass the sponge to the next person, and so on until one team fills up their empty bucket with water. That team wins.
Just before you say go, stop and tell the campers that, wait, there is one more rule! The wet sponges must be carried ABOVE their heads as they run back from the water buckets. They will get wet and have fun!