Non-Newtonian fluids let you run on their surface without sinking or drowning.
It is because the sudden impact of feet causes the surface to temporarily thicken.
Non-Newtonian fluids, unlike normal fluids, have viscosity that depends on shear rate, or the time it takes for it to undergo deformation when force is applied. When a sudden force is introduced to the liquid, like a slap on the surface, a quick hit or placing it on a plastic sheet over subwoofer speakers, the viscosity of the liquid increases causing it to thicken and the surface acts as a barrier. Which is why, the woman running on top of the the non-Newtonian fluid above was able to do so without breaking the surface.