High energy efficiency can be obtained by utilizing seawater as heat source water or cooling water of heat pumps. Then, we had developed the highly effective heat pump, which can use seawater directly as heat source or cooling water. In North Side Building of the Port of Nagoya Public Aquarium, the water temperature of huge pools for breeding orca, and belugas, etc, is adjusted with this highly effective heat pump system. In this paper, the energy saving performance, environmental preservation performance, and operation cost of the system are clarified by analyzing the operation data over a period of four fiscal years.