The video below shows some people making experiences in a pool filled with a non-newtonian fluid. A non-newtonian fluid is a fluid which the viscosity changes with the applied strain rate. Toothpaste is a Non-Newtonian fluid that we use everyday. By default, Toothpaste behaves like a solid. A minimum pressure must be applied to make the Tothpaste act like a fluid. It’s the same with the fluid in the pool below.