Looking for a way to kill time, cool down and get some scrapes on your knees while you’re at it?  Here’s the perfect game for that: Water-Soaked Knee Hockey.
Designed for backyard setups, the game has you sliding around on your knees on top of a water-soaked mat, swinging at an oversized hockey puck into a net at the end of the playing area. Being on your knees on a relatively small mat doesn’t make plenty of room for fancy maneuvers, of course, so expect to spend most of the time just trying to slide the other guy off the rink so you can get an open shot.
The Water-Soaked Knee Hockey Rink is a PVC playing mat, measuring 9 x 5 feet (l x w). The soaking part comes courtesy of thirty tiny nozzles built into the sides of the rink, which will spit out fountains of water (as high as 24 inches) when connected to your garden hose.  So long as you keep the supply of water constantly streaming at you, the mat should stay plenty slippery throughout your play.
Included with the rink are two inflatable goals (12 x 32 x 8 inches) for setting up at either end of the playing court, a plastic hockey puck and two plastic sticks.  The product page is careful to point out that the hockey sticks are “soft,” which means you can probably use it to engage in water-soaked knee stick fights, too, without hurting each other too much. Looks like a lot of fun.
You can score one from Hammacher Schlemmer, priced at $49.95.