“The world” back then also was something like a town and its surrounding villages. It probably just rained really heavy for a few days, flooded some village in a way that never happened before and the only explanation was “God’s wrath”.

I believe most of religious stories can be explained by people talking shit.

There was a flood after the meditteran salinity crysis, which happened partly due to lowered pressure in the nord causing the ground in the south to recede after the ice was gone (think of pressing in a balloon). There was a theory that the black sea flood (was half as big prior) due to this was what we know as the great flood, with humanity living mostly around there at the time, but i think it was refuted, because the flooding happened over generations there.

The thing with glacier seas happened mostly in scandinavia, gb, up there, creating the english channel (the heck? German it is Ärmelkanal).

There’s another, funner, theory, whereby a feedback loop in tectonic movement makes the plate boundaries heat up and the plates move ever faster (for a while till it calms down again). The ocean floor thereby becomes hot and more buoyant on the mantle beneath - so ocean floor rises and continents sink.

That theory is backed up by some proper plate simulation by a respected scientist, but as far as I know it was never developed past the initial simulation work and intriguing result.