Conventional wisdom says …
That most of Earth’s water is in the oceans.
I added the left column to this classic diagrams after reading The Story of the Earth by Robert M. Hazen
But did you know the mantle and core contain 80 ocean worth’s of water. Or in other words, all the water in all the oceans (and yes, I’m talking all seven seas) is a mere 1/80th of the water contained underneath the crust. What’s all that water doing down there? It’s hydrating the mantle and helping it move, which in turns drives the slow-motion movement of plate tectonics on the crust. By slow motion I mean even slower than your nails grow, or at a rate that makes a snail seem like a rocket ship.
The hydrated inner earth also helps its metallic core to spin. That both points your compass needle north and forms an electromagnetic force field that protects the planet (and all living things) from solar radiation. Neither Mars nor Venus have similar force fields, nor do they have plate tectonics.
Thank water for making both possible on earth.