Fluid Dynamics

This is an important bit of science: fluid dynamics.  Fluids do not compress, hence the stunning things possible with hydraulic power - power generation, the operation of backhoes and other heavy equipment, ocean waves. 

Another example is that if a stream of fluid, say from a 3 foot height, is directed at a stationary body of fluid, there is splashing.

Do this day in and day out, for example, there is an inevitable buildup of said fluid in the patterned wallpaper of your, say, bathroom.

Simple fluid dynamics.