Aquarium Full of Oil For PC Cooling
JaredOfEuropa writes "Forget fancy watercooled CPUs or complicated heat pipes. Annoyed with the noise of the forced-air cooling in his computer, this guy simply dumped his entire motherboard in an aquarium filled with mineral oil. (coral cache). No modifications were necessary; he even left the fans running to keep the oil moving about. The only thing not submersed in oil is the hard disk."
The problem with using "very pure" water is that it wants to become impure in the worst way. It's astonishingly reactive stuff.. It will suck atoms of carbon, silicon, and copper off a motherboard in its quest to become impure. And then, at some point, it starts conducting, and you're screwed.
So, you're partially right- you could use very pure water (for a very short time) until it managed to eat enough impurities to start conducting again.