Hot saltwater is the worst substance on earth, excepting, maybe, hydrofluoric acid. You really don't want to cool things with ocean water over an extended period of time. And filtering/purifying it takes vast amounts of power (e.g. reverse osmosis).

My 4 Cylinder Diesel Volvo Penta is cooled by sea water. There is an elbow that may have to be replaced every few years,

I wonder why they did not start with a freshwater body.