A slip and slide is always so easy to do and guaranteed many laughs. Go to your local paint supply store and get a heavy duty plastic tarp that folds out lengthwise at least 20-100′. Then, go to your local park with a small grassy hill and stake the tarp down on both corners at both ends. No need for a large amount of water, just fill a 5 gallon bucket up a the nearest drinking fountain, and right before some poor victim is about to drink, pour about a 1/4 of the bucket on the tarp and run and go as fast as you can. (Adding a tiny amount of bio-degradable soap to the tarp to help with any speed issues.) This may get boring after about four hours, so try standing up and skating down, shoot water guns at people as they go by, throw soccer balls at there feet, or go right after one another and train the whole slide . . . I recommend being the caboose, so you doesn’t end up at the bottom of the pile at the bottom!
A water balloon launcher, is always fun. Simply attach 10′ of surgical tubing, that’s doubled up, or in a circle to both sides of a funnel and send water balloons almost a half mile away. Give awards to whoever can “catch” the balloons, even a trophy who can catch it with out breaking it. Beware of up close launches, they can be deadly. . . or just aim for your big brother.
Water rockets are cool. Cut a wine cork in half, stick a ball needle through it so the end pops out on the narrower side. Fill a 20 ounce soda plastic bottle up 1/3 of water, then shove the cork and needle into the opening of the bottle. Pump up 15-25 times and watch it blast off into the air..or on your neighbors roof, on top of your school, wherever! Try to aim it up-right with your sandals or shoes your not wearing, then have everyone try to catch it. It usually has a mind of its own so prepare to knock into one another and the launcher will be sure to get all wet from the blast spray.
Water Ramp! Always my favorite, wherever there is a pond or lake with water 5′ deep or more close to the edge. Build a ramp and huck your bmx bike and yourself as far out an
d into the pond as much as you can. Be sure to secure the ramp to the ground/sand with a broad/wide base so it doesn’t move when you hit it going 50 mph. Then send it! The plans to build a sweet ramp are in my book, feel free to enlarge the ramp as big as you seam fit.
Monster Bubbles. Mix about 1/4 dish washing soap with 75% water in a shallow pan. Then take a wire coat hanger and bend it into a complete, closing circle, using pliers. Bigger is always better, I say. Dip the circle into the tray and run around the air will fill the bubble up and with a twist of your wrist, close the end and watch these huge bubbles dance across your yard! Try to lift a bubble up and over your friend’s entire body. Be sure that the wire circle is big enough to go around him or her. Then when it works, take a picture and call him bubble boy!