Turns out, walking on water isn't as impossible as it might sound - as long as you have the right kind of water. Following is a transcript of the video.
These people are "walking on water." The substance is a mix of water and cornstarch. The mixture is two parts cornstarch to one part water. It demonstrates the properties of non-Newtonian fluids. Non-Newtonian fluids are solid if you apply a sudden force and liquid if you apply a steady, slow force.
How can something be a solid and a liquid? In the mix, there are tiny cornstarch particles evenly distributed. When a steady slow force is applied, the particles have time to move out of the way. So the object slides through, as it would in a liquid. When a sudden force is applied, the particles don't have time to move out of the way. So the object is stopped, as it would be on solid surface.
What makes non-Newtonian fluids unique is viscosity. Viscosity is the rate at which fluid flows. Common fluids, like water, have a consistent viscosity, so they flow the same regardless of what force you apply. In Non-Newtonian fluids, viscosity can change. Apply a sudden force, and the viscosity rapidly increases, forming a semisolid surface.
What can you do on a non-Newtonian fluid pool? Jump. Bike. Flip. Whatever you do, just keep applying high force, or you'll sink right in!