Muf (Mr. Diver?), this 'proposition' is more complex than it 'looks to be' and not only includes 'evaporation rates' between 'saline' and 'pure' water surface interactions that cools 'surface water' for a given scenario, it involves the 'humidity and "temperature difference"' between the 'air' (gasses) and water/air immediately above/between the surfaces of these mediums for the gasses and water to 'interchange any energy' in question.
'Pure water' (or low saline inclusion) gives a 'lower density' for the 'body/surface region' of 'any "sea, or lake" (ignoring gravitational anomalies [other than the 'displacement rule'])' then this 'scenario' can only be 'disclosed/understood' by the day by day, hour by hour, 'collation and use' of data.
It would seem to me that the, 'lowest density' of the 'water body' is, "at the surface of the planet"' and' not disclosed' at 'when/where' we were told !
Kindest regards, Ray Dart (AKA, suricat).