What Atlantis?
Plato wrote a fictional story which was later picked up by the likes of Jules Verne.
What did, however exist was Doggerland:
Between 10,000 and 7,000 years ago, Doggerland was inundated by rising sea levels, disintegrating initially into a series of low-lying islands before submerging completely.
Evidence of human civilizations has been found in the area now flooded.
Evidence of Neanderthal presence was found.
Let’s see that map again: