Fill up some water balloons. Then, tie the ends of the tubing (they should both be on the same side) to a tree, pole, or anything else that is secure...
Make a wicked cool catapult that shoots water balloons really well without them exploding right away! You can buy water balloon shooters in stores, but they never work well and explode the water balloon as soon as you let go.
Step 1: Gather materials
You will need an old towel, or some sort of rag that you can cut up. You will also need a length of surgical tubing, exercise tubing will work here as well. Lastly, you will need two small scraps of wood and some duct tape. You will also need scissors to cut the rag.