Water is a magic substance, and why on that alone one could say there is a higher authority that the planet Earth ended up with so much of it.
Almost unique, it is most dense just above freezing, and less dense below, such that water freezes from the top down -- enabling much life in the oceans and inland lakes.
What matters here is its specific heat, higher than almost any other common liquid.
For that reason, a mixture with water is almost always recommended, and a waterless coolant cannot perform as well, unless there is some driving requirement that forces one to demote thermal performance.
