All you need is... sponge.

I had seen this idea quite some time ago... it has been EXTREMELY hot here lately so I thought I would have some fun with the kids. To make six sponge balls, simply cut 4 large sponges into strips (I used the short width vs. the height to get more for my money). By the way, the sponges cost $2.00 total... a cheap activity! Gather the strips in groups of 4 or 5 and tie them in the middle with string.
We used two buckets of water and set up a "battlefield" in the backyard. BOMBS AWAY!!!! We had so many giggles and the sponges were just the right size for the kid's hands. I do not have pictures of the actual battle because there was WAY too much water for the Canon Rebel AND I was laughing WAY too hard to take the time to stop!
We rewarded the entire team with some leftover cookies... that part is optional.