Oobleck is a liquid and a solid at the same time and can be very entertaining. To make it you will need:
1. A bowl, container, or a pool
2. Corn Starch
First you get a container of some sort,
Then fill it with water.
Then add cornstarch until you can run and jump on it (or flick it without your finger touching the bottom). Notice if you just stand, or put your hand in it it will slowly sink. If this happens you now have Oobleck.
I would show you a video but they are all "no longer available"