Here is an atmospheric treatment of the subject by indie history buff channel: History Time - "How Doggerland Sank Beneath The Waves (500,000-4000 BC)"
Great podcast, just listened while doing the dishes. It is fantastic to consider our limited time on Earth here, contrasted with the other current article today on writings about what to do with our time on Earth.
"About 8500 years ago, a massive freshwater lake in North America called Lake Agassiz, formed by melting glaciers, drained suddenly into the sea. What had been gradual sea-level rise accelerated, and seas rose a few meters within decades." Pretty crazy!
It seems plausible that a relatively slow increase (that is, compared to a supposed catastrophic flood) over tens of years, well within a single generation, could turn into, "and the entire world flooded overnight" within a generation or two of exaggerated story-telling. I mean, most religious fables are probably nothing more than exaggerations of real events, if not outright fabrications.
That kind of increase might very well be noticeable from year to year, and after 10 years you might come back to where your lands used to be only to find the sea has taken it over entirely.
And when legendary treasures are discovered, they often turn out to be a box of junk. The story grows in the telling. Especially if there's nobody around to contradict.
Laymen were nor very aware of what was going on mere hundreds of kilometers away. It is very possible that either this meltdown or Bosporus overflow was interpreted by some as "everybody died".
Something to keep in mind is that different flood myths around the world might have been inspired by unrelated floods. It was not necessarily one global flood that inspired flood myths around the world.
https://www.bbc.co.uk/programmes/m0006707