Inspired by the Balloon Powered Car, this is a Balloon Powered Hovercraft.

1. Inflate a balloon

2. While pinching the balloon shut, put the stem of the balloon over the inlet at the top of the hovercraft. This is tricky but it can be done.

3. Place on a smooth, flat surface.

4. The hovercraft will float a short distance above the surface until the balloon deflates.

Also useful for determining just how level your table, floor, etc. is, since if there is any slope to the surface whatsoever the hovercraft will drift downhill.

Won't work well on rough surfaces like carpet, grass, etc.