What I understand from the bible is that the land emerging from the water was a sole land, the continent known as Pangaea
No rain happened but vapor coming from underground this huge continent. A river which divides itself in different branches was also coming from the underground.
At one point, a crack in land caused the flowing of water from the underground going up. This water should have been hot, as it is understood that caused vapors escaping from small cracks on land.
This water might have also lots of sulfur. The fast coming up of water like a gigantic geyser reached to atmosphere at the point of causing condensation, and by consequence rain.
Earthquakes and tsunami should be present and the whole planet must have been changing its tilt.
The continent before the "mabul" (known as flood or deluge but in Hebrew "mabul" means desolation by cause of water) didn't have the huge mountains of today, it was different. The waters covered the sole continent for months until the water receded and returned back to the underground rivers and lakes.
The bible says that one descendant of the family of Shem was named Peleg (a name meaning "division") because in his days the earth was divided.
This is to say, the crack expanded and caused other ruptures and the whole Pangaea was divided in several parts known today as continents.
The ratio of speed of the division should be fast, causing lots of earthquakes for centuries. The formation of new lands and mountains is what happened with the motion of the parts of the former huge continent.
Humans and species which found areas were to live before the division of land were trapped in the new partitions and acquire their own characteristics in accord to the new environment to which they were exposed.
In certain areas, the exposure to chemicals and gases caused the birth of humans with defects, also caused changes in other species, including plants.
It was a process of extreme changes.
Notice the difference of people's characteristics from the first civilizations. At one point, they grouped themselves according to their own similitude.
The bible shows how careful was Abraham and Issac to choice the woman for their sons, telling them to look for women of the same "family", because two reasons, race and belief.
So, the genetic similitude is obvious when the whole humanity comes from the same family, and the differences are just consequences of living in different environments.
There is no any evolution in this process, but survival in front of the new environment.
The species don't create the changes, it is the environment the one that changes the species appearance, diet, behavior, etc.
On the other hand, it is a fact that any genetic variation in humans, like additional tails in chromosomes or conjunctions cause the ape alike characteristics in the affected humans.
When you find fossils of humans with certain close appearance to apes, such is a birth defect caused by the environment in that area.
There is not a single observation that same chromosome tails and conjunctions in apes will cause them human alike characteristics.
Facts rule, and facts indicate that there is a greater possibility that apes are descendants of humans rather that humans being descendant of apes.
(Note that the theory of evolution was invented in base of ideas from Kant and others, who established that humans are descendants of Chimpanzees and Orangutans before Darwin, and in 1920's the hypothesis of humans as descendants of lemurs became the new approach.
Today, evolutionists try hard to cover up their silly genesis, and claim that their theory is not about being descendants of apes when such is the main purpose of the theory of evolution when was recognized as a theory).