The princess of the city of Ys haunts Brittany as a mermaid

Dahut is a character from the legend of the city of Ys, the most famous tale in Breton folklore. According to tradition, she caused the submersion of her city by the ocean because of her sins. She did not perish in the catastrophe however and continues to haunt the bay of Douarnenez in the form of a mermaid.