Whale S600 120V 6 Gallon Galvanized Marine Water Heater wRear Exchange This Whale boat water heater is ignition protected and features a rear heat exchanger. Constructed from marine galvanized steel for excellent corrosion resistance in marine environments. The front and rear hold down brackets are welded to the inner tank for a sturdy hold. An integrated pressure relief valve and temperature monitor safety controls keep your water heater from overheating. To prevent accidental freshwater contam