I’ve learned all sorts of strange facts about eels by doing crossword puzzles. EEL is a super common crossword answer. If the clue references some aquatic creature and the answer is 3 letters long, very likely the answer is EEL.

That's crosswordese for you - https://en.wikipedia.org/wiki/Crosswordese - there's also ERNEs, AUKs, TERNs and ORCAs out at sea