Explain why oceanic crust has ocean water on it. Where did the early Earth get its oceans and air?

Question

Explain why oceanic crust has ocean water on it. Where did the early Earth get its oceans and air?

Answer 1

The continents are floating on the mantle which, while not liquid, is ductile enough to move and flow on a very long timescale. The ocean crust is dense so floats below sea level. Continental crust floats above sea level because it is much lighter.  

The atmosphere and a portion of the water was outgassed by volcanoes and subsequently modified by microbes. Additional water came from comets during the heavy bombardment portion of the Hadean.

Answer 2

meteorites... Mars has water too... its just frozen at the poles...