Cruisair Seawater Pumps Cruisair offers a wide selection of seawater pumps suitable for any air conditioning installation. For most vessels, Cruisair centrifugal pumps are recommended. These are not self-priming and must be mounted below the water line. For houseboats and other shallow-draft vessels where the pump must be mounted above the water line, either the PJ250 or P1500B-SP self-priming pumps must be used (special order item). When more than one condensing unit is to be operated with a single seawater pump, a pump relay must be used.