This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Fish-man (Cantabrian)
The fish-man of Lierganes is an entity of the mythology of Cantabria, located in the north of Spain. The fish-man would be an amphibian human-looking being, who looked a lot like a metamorphosis of a real human being who was lost at sea. His story was examined by Enlightenment writer Benito Jerónimo Feijoo, who claimed that the story was true.
Fishman is another legend told of in Northern Spain (and goes back to 1650). The Fishman is reported to be a humanoid fish-like creature of incredible strength and size (6 to 8 feet). One was supposedly capture in the 1670s and even lived with the family of the Fisherman who snared it with his net. The creature can communicate somewhat.