By The Sea (слэш)

Little orphan Harry was raised by the sea by his cruel aunt and uncle. His uncle is the mayor of the fishing town. He was told his whore of a mother got pregnant by an unknown man and that she drowned herself in the ocean out of shame shortly after his birth.
Harry is kept away from the ocean by his aunt who seems terrified of the water, but she is actually aware that Harry is not fully human though she has kept it a secret from even her husband out of fear of being punished herself. However one day, Dudley and his friends chases Harry to the cliffs overlooking the ocean, and Piers pushes Harry into the ocean. Harry thought for sure he would drown, however under the waters he transforms into a mythical mermaid.
Harry travels alone in the sea for a while, but he is found by Mer-King Grindelwald's patrol, Severus Snape and Bellatrix Lestrange. Severus recognizes Harry for who he is - the missing child of Lily Evans whom the Mer-King had killed to punish James Potter for daring to have a relationship with a human. What kind of life waits for Harry now?