In 2014 scientists discovered a very interesting find. The lead scientist noted there is a vast reservoir of water under the earth's surface.
The money quote from the article.
"If [the stored water] wasn't there, it would be on the surface of the Earth, and mountaintops would be the only land poking out," he said.
http://www.natureworldnews.com/articles/7560/20140613/vast-underwater-ocean-trapped-beneath-earths-crust.htm
You might find this book interesting. You can read it free online or download a free zipped copy for later:
The Biblical Flood and the Ice Epoch
The author touches on that subject as well as how it was released by a planet sized object passing earth at just the right distance (The Roche Limit).
A bit technical at times but an interesting book.