Such great things come out of MIT's media lab: one of their visitors has built a water-based computer.
This could come in handy in the event of a massive electromagnetic pulse. However, I suspect most people would have other matters on their mind at that point.
In all seriousness, this is a wonderful project. Like other mechanical algorithm devices, it allows the fundamental procedures of computation to be animated in space, relieving the burden of mental modeling from the executor.
But remember, if you're seated in the first six rows, you may get wet during this subroutine.