Where Did Earth's Water Come From?

(via TEDEd) Water covers over 70% of the Earth, cycling from the oceans and rivers to the clouds and back again. It even makes up about 60% of our bodies. But in the rest of the solar system, liquid water is almost impossible to find. So how did our planet end up with so much of this substance? And where did it come from? Zachary Metz outlines the ancient origins of water on Earth.