The mathematical description of fluids like water goes back to the Swiss mathematician Leonard Euler in the middle of the 18th century.
If we think at a discrete level, for instance in terms of pixels, the motion of water looks very much like a very fast succession of permutations exchanging pixels, a little like a "melting rubik cube".
We will discuss this analogy in more details, in connection with the mathematical theory of optimal transportation and its numerous applications.