Summertime means rising temperatures—and, often, rising tempers. If your friends and family want to beat the heat without beating each other, there's a surefire option: squirt-gun fight! But shelling out for a few $20-or-more water weapons can rapidly thin a wallet. That's why you should take matters into your own hands, visit the hardware store, and exercise some garage ingenuity to build an inexpensive yet durable arsenal of Waterzookas. Popular Science likes this version from the website Instructables.com, but we tweaked it to stay current with the latest water-gun technology. Follow these instructions to keep your cool.