The water came from within the earthThey've known about underground springs and rivers for millennia. There isn't enough water on or in the planet to cover the entire earth.
But also from the skies. For forty days and nights and one has to think it was awful rain ..
It's rains,here for 3 hours straight the stress are flooded
And we have storm drains,running into canals.draining into the ocean
There are locks from the west also draining water(the water management people usually manage to mess things,up near October.they send water east when it was supposed to go south as well..we get even mire street floods And other rainy season Times..But that's a whole mother story ...)
The earth was different then
I do believe ....there are flood accounts in a lot if civilizations ..
People descended from the sons were dispersed all over ..only one line of one son became the Jews...