Medieval story-tellers/historians wrote that in the day of king Gradlon (circa 500 a. d.), a barrier which had been built was keeping the ocean out of Douarnenez bay (western tip of France) where flourished the kingdom of Ys, but the mouth of that bay is 12 miles wide and about fifty feet deep, so that would have been some barrier and where’s the evidence of it? Obviously that kingdom was flooded when the Ice Age ended, toward the end of the century-long sea level rise of about three hundred vertical feet.
