I see this thread is over a year old. So I may be repeating what others have already said. If so, my apologies.
That the entire earth could be covered with water is fantastic. Many narrow minded folk would say it was incredible / impossible. Some of them are unbelievers (in God) and they pooh pooh the validity of the flood of Noah. Seashells embedded in the tops of the highest mountains to them only means they were ancient sea bottoms before upthrust into mountain peaks. Others are believers but also cannot grasp a global flood so they try to explain Noah's flood was a local even in Mesopotamia... kind of like the movie Evan Almighty. But when you factor in all the evidence the Bible teaches about the flood, and consider that the average level of land on the earth its below sea level... not to mention the water locked in the frozen poles of planet earth... it's not such an incredible thing after all. In fact, when you realize the earth was described in Genesis 1:6-8 a planet with a vapor canopy (five of the planets in our solar system have canopies to this very day) which collapsed during the 40 day 40 night rains.
Before that downpour there was no rain on the earth. A mist would rise up from the earth in the cool of the day.
Ancient civilizations all have a great flood legend. They vary due to the many generations of human interpolation... but they validate the flood itself... the actual eyewitness account we have in Genesis (as dictated to God's scribe Moses).
The Fossil record supports a sudden deluge. Fossils are flash formed (not over long periods of time) and the fossils of land and sea creatures litter every lay of water sediment... even in the tallest mountains.
Noah's ark was spotted regularly during overflights in world war 2...
The Institute for Creation Research has a vast amount of information about the Genesis flood in a library and museum that was once located in San Diego, Ca. I personally spent many hours there in the mid 1990's. In it they have a replica of the barge Noah built. The average size of the animals taken aboard is that of a sheep. Noah did not have to take every variation of species but every kind (wolves for example which would later produce every variety of dog and wolf there is). So the size of the ark was not a problem. The gist of the time spent aboard the ark was that the animals hibernated.
The subterranean vaults burst open revealing deeper ocean bottoms and the collapse of land masses over them as they gushed and the tectonic plates slide around and collided under the global weight of the water alone.
I am speaking in very general terms here as I am quite rusty on the subject. 15 years ago I could have documented every syllable.
I have a theory about an event after the flood but was a delayed result of the flood... that the lost continent of Atlantis is essentially south America. That the entire American continents (North, Central, and South) broke away from Africa and Europe. Atlantis was a population center at the time and some of the ancient central and south America dwellings were at one time accessible to the Africa and the Middle east before the break away. Europe and North America were not population centers then so the focus was on what we know today as Mayan and Aztec cities etc.
This happened in the lifetime of Peleg whose name means divided. And as the continent moved west it would appear to sink into the ocean as it went over the horizon.
As I said, just a theory.