Over a decade back there was a company that sold air cooling devices for cruising sailboats. A sailboat at anchor is chronically short of electrical energy unless one runs a generator, which has its own trade-offs. The essence of operation of these devices was to pump seawater up from some small depth (maybe 15' below the surface), through a radiator, and back over the side. The radiator had fans to blow outside air through the radiator and into the cabin. The company subsequently went out of business as far as I can tell. I'm thinking of trying a DIY implementation, but before I do, I thought I ought to check whether they went bust because of bad engineering/physics or bad business judgement. Assuming the following does not look too much like "homework": Suppose that I have a standard automotive radiator, copper (because of the sea water if for no other reason), and I pump (say) 4GPM (15LPM) of seawater through the radiator, where the seawater is 10°F (6°C) below the air temperature. Air would be moved by some small "muffin" fans. What is a reasonable expectation for heat extraction or, alternatively, what kind of temperature drop is it reasonable to expect from ambient air to exhaust air? If I see 5°F temperature drop, it might be worth doing. The water flow rate above is the flow rate of a common marine pump and is arbitrary. I kind of suspect that building some kind of shroud that would pass the air multiple times through the radiator would not pay off, but would appreciate confirmation or correction. I have some college physics, but the textbook was printed on parchment. Thank you.