The wonderful thing about computing with water is our familiarity with this ubiquitous substance. Water is everywhere that we are. As I look outside my house window at the ice melting, I see melted water drops and then a spreading of water. I can also see water and trapped air bubbles underneath the ice as it melts on the road surface. Familiarity with water stems from our drinking it, bathing in it, and watching it flow in rivers and streams. Water can also be used, via analogy, for performing computations. Water is a natural integrator - turn the tap (the derivative), and capture the tap water into a container (the integrated derivative). Vladimir Lukyanov designed and built several water integrators in Russia and the USSR, and extended them to solve partial differential equations (PDEs). The above image is from Science and Life: a two-dimensional hydraulic integrator. The machines can be found in the Polytechnic Museum in Moscow.