I really like the idea of a natural water source. Something like a liquid cooled rack. Many gaming pcs are liquid cooled anyway and if there were a natural spring close enough to plumb water into the data center, this water could pass through the actual frame of the rack drawing heat from the bottom and carrying it away as well as having outlets at each server to push liquid through the internal cooling system and remove the heated water at the same time. I’m imagining this much like an automobile radiator. This liquid refreshment as well as proper ventilation, would work great as far as I can imagine.
Let me know when someone actually tries to implement this!