ancients, once collected in proto civilizations, mostly desired to be living near water,(resources, travel, protection etc)
MAny places with flood myths have been documented to actually sustain periodic disastrous flood events. Its an easy jump to be so "centric..." of ones own "Hood" that the invention of a flood myth has some bases in evidence. Sorta like SCylla and Charybdis.
Several good texts have been written about the evidence behind catastrophies associated with several civilizations.
Even in North America the several native nations have flood myths slightly different but all full of lessons for human beings to learn.
The real hot-bed of flood myths though is the area from the East Mediterranean, to the LEvant and to the Guptah area of India, SE Asia and on to Melanesia.
I dont think that e are yet able to red any legends from S America or S Africa . We just dont have a way to decode except for Subsahara and the Scarp Countries to the Niger.
All of em have one thing in common--waterside residences