Read more, fantasize less. This is an instance of brute force engineering, where they are constructing giant neural networks in which each neuron is the equivalent of its own computer center. Astronomical number of neural interconnections. The thermodynamics of information processing means they need a lot of power to drive the process. They don't need water, per se; they need cooling. They can get cooling from industrial level refrigeration, but that takes more power, so water is the cheap and easy way to do it. And, as this is a footrace, there is a crash program urgency about it. It's a big bet that this isn't a huge waste of time, money, and resources.