The super absorbent fiber weave technology of the mesh towel regulates the water inside and ensures water retention, so it's treating it kind of like an air-conditioner, and within seconds you get cooler.
Like sweat on you skin, when water evaporates it cools. Any ole cotton or microfiber towel would work, but not as well design to maximize evaporative cooling or comfort.
If you are sweating a lot, rinse the 'salty water' out from time to time. Salt reduces evaporation/cooling rate