Why does the evaporation of sweat cool down your skin?

So sweat helps cool you down two ways. First, it makes your skin feel cooler when it's wet. And when it evaporates it removes some heat. But sweat will only evaporatoin an environment where there isn't much water in the air.

The characteristics of groundwater is said to be: are weak turbiditya constant temperaturechemical composition and almost overall absence of oxygen.