Question

What percentage of the earth is made up of water?

Answer 1

About 71% of the Earth's surface is water, though it only makes up around 0.02% of the planet's total mass.

Explanation:

The crust is very thin compared to the rest of the Earth, about 25 miles on average, and the ocean is rarely 10, compared to the 6400 mile thickness of Earth.

Also, water has a density of about `1gcm^-3` at room temperature and pressure, while granite is around `2.7gcm^-3`. While not all rock on earth is granite, it is a fairly good example that rock is heavier in the same volume than water is, so water would not make up a vast majority of the Earth's mass.

This does not take into account the amount of water vapour in the atmosphere or below the surface, because they are difficult to measure and in the grand scheme of things would not make a lot of difference.