Because our oceans are so shallow compared to the sheer mass of the earth, all of that water—all 71% of it—only makes up for about 0.02% of the mass of the Earth! It's hard to believe that our oceans are shallow, but they are, compared to the diameter of the Earth as a whole.
Our planet is about 40,000 km (24,900 mi) in diameter, while the oceans at their very deepest are just 11 km (6.8 mi). While going 11 km straight down may seem like a lot, it's nothing compared the Earth as a whole.
Of all of that water, only about 2.5% is fresh water. The rest is contained in oceans. And of that fresh water, and amazing 67% is frozen! If you were to melt all of the frozen water and let it go in the seas, the sea level would rise about 2.7 km.
