Mt. Everest did not exist at that point in time. A christian geologist wrote a book called "In the Beginning" and theorized that the flood event was due to cooling of the mantle, which subsequently cracked, releasing the 'fountains of the deep' and rapid condensation of the saturated atmosphere. The broken crust then shifted and slid into other plates and caused the mountain ranges we now have. Something to ponder.
How long did it take them to get all the animals and birds in the ark?
Approximately 75 years, but that is an estimate based upon the dates given in Genesis.
What’s also interesting is the fact that there are real underground bodies of water, that are known to exist on Earth today, such as the guariana aquifer under Brazil. To know how much fresh water that is, it’s estimated to have enough fresh water to supply 7 billion people with drinking water for 200 years.