Oral traditions of Australian aborigines record events going back at least 7,000 years, and as much as 13,000 years, old. Sea level rise dating that far back displaced people living on what is now seabed, called Sahul, between New Guinea and Australia, obliging people who lived there to move to Australia, causing conflicts whose negotiated resolution is still passed down.

20,000 years ago, the sea level was 400 ft lower. People had already lived there for tens of thousands of years. Even 13,000 years ago there were still millions of square miles now inundated. If there were not legends reflecting such an event we would need to know why. As it is we do have such legends, everywhere. The flood did not recede; we call it the sea now. It happened gradually, but large flat areas would have been covered in a generation.

https://en.wikipedia.org/wiki/Meltwater_pulse_1A#/media/File...

https://en.wikipedia.org/wiki/Sundaland#/media/File:Map_of_S...

What was Sundaland is girded by what are now Indonesian islands. The Yellow Sea west of Korea and the northern South China Sea off Viet Nam to Taiwan were dry land. Territory stretching out hundreds of miles around India, particularly to the west, south of Pakistan, shows evidence of construction (visible right before the big tsunami). Britain was not an island; we call the land where the North Sea is now Doggerland. The whole Persian Gulf was dry land, south of Mesopotamia. The oldest cities there border the gulf.

https://en.wikipedia.org/wiki/File:Doggerland3er_en.png

See orange areas: https://en.wikipedia.org/wiki/Bathymetry#/media/File:Mid-oce...

Zero.