Oobleck is a mixture of corn starch and water which makes a non-Newtonian fluid. What that means is that it acts as a solid when pressure is rapidly applied to it – so you can run across a pool of it for example, or sink into it if you stand still.
TheBackyardScientist team did some absolutely necessary scientific investigation into the properties of oobleck when exposed to pressure: cutting into an oobleck balloon with a chainsaw, firing into it with a BB gun and finally shooting it with a propane-powered golf ball cannon.
Cue non-Newtonian waterballoon explosions…
* As a reminder of what running on oobleck looks like:
Fun fact: oobleck takes its name from the Dr Seuss book Bartholomew and the Oobleck.