I am stuck on last clue of which there is a Cryptic and quick clue(answers are the same)66A (Cryptic)Mermaid's best friend(7)......(Quick clue)Marine creature(7). I have ?O?F?S?. I'm thinking boxfish,codfish,dogfish etc but what has a mermaid got to do with it.A dog is a man's best friend not a Mermaid's??
Help appreciated please.