Try making this amazing Mini Miss hovercraft from Blast Lab.

What to do:

1. Take a 2p sized piece of sticky-tack and roll into a thick sausage long enough to go around the outside of the sport bottle cap.
2. Wrap this sticky-tack sausage around the bottom of the sport bottle cap making sure that the sausage is not completely on the outside or inside of the cap, but half way between.
3. Take the cap and sticky-tack combo and place over the middle hole of the CD on the printed side.
4. Squish and squash the sticky-tack so that the cap is firmly stuck in place.
5. Take the balloon and inflate it.
6. Make sure the sport bottle cap is closed and place the neck of the inflated balloon over the cap.
7. Let go and the balloon should stay inflated - if it doesn't then make sure there are no gaps in your sticky-tack.
8. Your hovercraft is now complete. Take it to the table or smooth floor and carefully lift up the top part of the sport bottle cap so that it's open (make sure you hold the cap down with one hand as you do this otherwise you'll just lift the cap off completely!) and give the CD a push. It should glide across the surface only stopping when the balloon completely deflates.
9. Get your friends to make one as well and then see whose can go the furthest.

When the balloon is inflated it wants to deflate, so as soon as you open the sports bottle cap this is what it does. The air that was inside the balloon is forced down through the sports bottle cap to underneath the CD. Here it creates a cushion of air for the CD to glide on. This cushion of air pushes the CD slightly off the table top or floor, meaning that there is less friction. And less friction means our hovercraft can travel further without coming to a stop.