Refers to a cooling system that uses water. Similar to a car, systems for electronics circulate water in a loop, through a cooling radiator, to all of the heat sources. In personal computers, the hottest devices are the CPU chip and GPU chip (the processor on the display adapter). Every second, there are billions, trillions and quadrillions of transistor switchings taking place, which generate a substantial amount of heat.

Faster or Quieter
Water cooling systems appeal to people who like to push the envelope and build fast personal computers with the fastest chips, because water cooling is very efficient. They also provide an effective heat system without fan noise. Water cooling is not new to computers. Some early computers and many large mainframes used water cooling systems for years, but eventually gave way to air cooled after chip technology made them much smaller. Water cooling a room-sized computer required an extensive plumbing system.