Water cooling for a computer uses a combination of “water blocks”, radiators, fans, coolant reservoirs, pumps, hoses, and connecting fittings to cool your computer. Water blocks are pieces of heat-conductive metal like copper or aluminum that are filled with hollow tubes and channels.
Water has a higher specific heat capacity, meaning it can absorb more heat energy than air can. Water also has a higher thermal conductivity than air, meaning it can move heat faster than air can.
There are two reasons why a computer might need the increased heat capacity and thermal conductivity of water.