Earlier this week AnandTech took a look at two self-contained water cools: the Xigmatek AIO and Evercool Silver Knight.
Several new "self-contained" water coolers have shown up over the past few months. Water cooling is another ambient cooling method, like air cooling. The water temperature cannot drop lower than the room temperature, where TEC and phase-change can actually chill below the ambient temperature. This is why they are referred to as sub-ambient cooling. Water cooling is normally considered superior to air cooling because water can normally hold low temperatures for a longer period of time than air. Water is a much better thermal conductor than air and it is theoretically a better cooling vehicle.
There are many high-end water cooling solutions with water-filled tubing that runs from CPU blocks to radiators for cooling and reservoirs for storage, and pumps for moving the liquid. The water systems are usually complicated, somewhat difficult to install, and plagued with the fact that water and electricity don't play well together, so a leak can destroy a computer system. This is where "self-contained" comes in. The water system is sealed, and the radiator, pump, fan, heatpipes, and fins are all together in a package about the size of a heatpipe tower.