In the images from outer space blue oceans cover nearly three quarters of the surface of the earth. All but 3% of the water is salty. Most of our fresh water is locked in polar ice!
In understanding the water cycle we can see that evaporation is constantly drawing water up from the oceans into the atmosphere and eventually precipitating back down to earth as rain.
In the illustration to the left you can see all of the surface water rolled up into a ball on top of the mass of the planet.
Just to the right there is a much smaller blue ball that represents available fresh water. That tiny blue ball is our most precious resource!