This Illustration by Jack Cook shows the total amount of water on earth compared with the mass of the planet.
Charles Fishman notes:
The total water on the surface of Earth (the oceans, the ice caps, the atmospheric water) makes up 0.025 percent of the mass of the planet—25/10,000ths of the stuff of Earth. If the Earth were the size of a Honda Odyssey minivan the amount of water on the planet would be in a single, half-liter bottle of Poland Spring in one of the van’s thirteen cup holders.