What do you mean with water cooled? By a normal water cooled system you have a radiator to dissipate the heat, this way you still need fans on these radiator. Other thing you can do is a submerged system. But a far as i know you still need some movement of the fluids in the tank with some sort of pump or fan.

The effective heat a rig will generate is the same because the Watt's the rig consumes stays the same. You only move the heat away from the source more easily. So it stays cooler.