Your answers are here...
https://bitcointalk.org/index.php?topic=346134.0You can do it on a smaller scale with mineral oil in a fish tank and pumping it through a radiator with cooling fans using standard PC cooling parts.
The reason fully immerse it is to get cooling to every component (no cooked VRMs, caps or RAM) and transport the heat and fan noise outside.
I see many people put a cooling block on a VGA card, the GPU is nice and cool, but they forget the fan cools the other components too, and they melt them when they overclock!