Non-Newtonian Fluids

Perhaps you've fooled with "goo" or "gack" ... a mixture of water and cornstarch which behaves as a solid or a liquid under different conditions.  I've seen demos of people dipping their hands into, or standing upon, buckets of this stuff. 

The technical term for this property is "dilatant" or a non-Newtonian fluid.

Here's what it looks like when you have a big budget and someone else to clean up the mess!

(from freethoughtblogs.com/pharyngula)