Ker-Ys was a wonderful city, full of splendiferous palaces, temples and houses. Ker-Ys was situated somewhere in the Bay of Douarnenez on the western end of Brittany. On V century King Gradlon rules over the kingdom of Ker-Ys. He had a beautiful daughter, named Dahut. She lived a very dissolute life. Her last lover was the Devil Himself. As a pledge of love he asked her to steal and to bring to him the golden key that his father kept around his neck. This key allowed to open the lock protecting Ker-Ys against the furies of the ocean. Once he got the key the Devil opened the lock and the flood submerged the City. All the inhabitants were drowned.
Gradlon succeeded to escape, mounting his fast horse, Morvak, which ran quickly that the flood, but the Princess, Dahut, died...
Would you believe the fishermen who say that when the weather is clear and the sea very calm, they can sea below their boats the top of the golden temples and palaces, and hear the beautiful voice of Dahut calling them ?