The temperature of sea water is lower than the outside air temperature in summer, and higher than the outside air temperature in winter. Therefore, high energy efficiency can be obtained by utilizing sea water for heat source water or cooling water of heat pumps. Then, we had developed the highly effective heat pump, which can use sea water directly as heat source or cooling water. In the Port of Nagoya Public Aquarium, the water temperature of huge pools for breeding orca, belugas, etc., is adjusted with this highly effective heat pump system. In this paper, the energy-saving performance and environmental preservation performance of the system are clarified by analyzing the operation data over a period of four fiscal years.