Standing on the seashore, watching waves roll in from over the horizon—it is easy to see the ocean as something timeless. Our ancient ancestors certainly did. In numerous creation myths, a watery abyss was present before the emergence of land and even light. Today we realize that Earth's global ocean has not been around forever. Its water—as well as every drop of rain, every gust of humid air and every sip from your cup—is a memory from eons ago, when the seas literally fell from the sky.