Ever bathed in sea-water below 0°C?

I have. And most coastal ppl in Northern Europe are aware, you cool out much quicker in water than if you' simply cover yourself in Ice or snow. Cooling a solid object quicker, already saves time. But water's also a better insulator than Ice.

Ice melts at >0°C. Saltwater doesn't. So no endothermic reaction like in Ice neither. Best way to cool drinks quickly isn't Ice, but cold water. How do you keep below-zero water from forming ice? Salt!

tl;dr - Pretty common knowledge where I'm from (Ger/DK).