A water source heat pump operates much like a traditional air source heat pump except that it extracts and dissipates heat by way of water instead of air. This is certainly not a type of home comfort system that will be available to anyone, but if you live in an area close to a well, lake or other natural water source, it may be an option worth considering.
Water source heat pumps, on the other hand, work on basically the same principle as air source heat pumps, but they extract heat from a body of water rather than the air. They do this by cycling water through a system of pipes that is laid out at the bottom of a body of water. As the water cycles through, it gathers heat from the lake or reservoir and then carries it back to your house.