I can hear this photo.

The reason for adding the salt to the ice is the reason we add salt to ice in ice cream makers. The salt causes the ice to melt, which is an endothermic process. This means it needs to get energy from somewhere, and that somewhere in ice cream making is by cooling the cream/custard. In the case of the fishermen, it just means the fish is cooled quickly.

The boiling point is just the point at which a liquid can no longer remain a liquid. It can become a vapor at much lower temps, below freezing even.

One factor to consider is humidity. The air can only cool to the dew point and at that point there is an equilibrium. Instead of getting colder, things just get wet. Humid air has a higher specific heat capacity than dry air, so the same amount of solar energy will heat an equivalent volume of air to different temperatures.

I lived in Bermuda where the humidity is always high, but the diurnal range is greater in winter when the humidity is lower.

Here is light reading and formulas: https://www.engineeringtoolbox.com/amp/enthalpy-moist-air-d_683.html