Cooling and heating with a reverse cycle marine heat pump is a simple process of moving heat from one place to another, by using a refrigerant and a mechanical method. The heat is either removed from the boats interior air and disposed into the seawater or removed from the seawater and circulated into the boats living area. Refrigerant reacts easily to temperature and pressure, while changing states similarly easy (liquid to gas, gas to liquid). When a change occurs in the state of a refrigerant, heat is either absorbed or released; we use compression or a change of pressure to make this happen.