Water covers about 71 per cent of Earth’s surface, yet the entire hydrosphere accounts for only about 0.02 per cent of Earth’s mass — almost all of the planet’s mass is rock and metal beneath it

From SpaceDaily

Ask most people what Earth is made of and, somewhere in the back of the mind, the answer is water.

We picture the blue planet, the oceans wrapping most of the globe, and we quietly file water under “main ingredient.” It’s natural but almost entirely wrong. Water is what Earth wears, not what Earth is.

Two numbers reset the whole picture. Water covers about 71 per cent of the surface. But by weight, it makes up only about 0.02 per cent of the planet. The blue we see from space is real, and it dominates the view. By mass, it barely registers.