Here is what happened - a slide presentation:
http://www.threeimpacts-twoevents.com/wp-content/uploads/2013/08/COMET-IMPACT-ANALYSIS-AND-EFFECTS-20Aug2013.pdf
There was a world-wide flood, and it was created by waters delivered by a massive comet that struck in what is now the Southern Ocean.
Or maybe more likely a storm of comets and other debris that originated from the fountains of the great deep inside the Earth. So massive it even broke open the atmosphere surrounding the Earth [see Genesis 7:11].
Center for Scientific Creation - In the Beginning: Compelling Evidence for Creation and the Flood
http://www.creationscience.com/onlinebook/IntheBeginningTOC.html
Dr. Brown was inspired to formulate his hydroplate theory by Whitcomb and Morris as well as the Bible.