Oobleck!
Tonight we were watching an episode of Ellen (The Ellen Degeneres Show). She (Ellen) had a guest on who was showing us a neato thing with cornstarch and water. My friend tells me in the sci-fi community this stuff is known about, and is called oobleck. It's neat. You apparently just mix corn starch and water. If it's at the right proportions/consistency, it is called oobleck. If it is in motion (pressure is applied), it firms up to a solid-like substance. But if it is still, it is a liquid. Fascinating!! I want to get some corn starch and try it!! It's solid-like enough to support the weight of a human being balanced on one foot - provided they keep moving. If they run, it'll support them. If they walk, they'll sink into it.
The wikipedia article is here
And here is a neat display of folks walking around on it!