If all of the earth’s water – salt and fresh water – would be collected into a single sphere, it would be this big compared to the size of the Earth:
Illustration by Jack Cook, Woods Hole Oceanographic Institution
(source, source)
The sphere includes all the water in the oceans, seas, ice caps, lakes and rivers as well as groundwater, atmospheric water, and even the water in you, your dog, and your tomato plant.
A telling visualization of the world’s water crisis, albeit with a hint of alarmism, and an ideal occasion to link back to some of my older posts about the water crisis: here, here, here, here and here.
