(idiomatic) "a fish who's found water" → In one's element, a duck to water.

pretty, gorgeous, beautiful / clear, clean, pure / clean, not dirty / tidy, neat, everything put away / fair, impartial, of clear conscience

lip service; promising but empty talk / skillful completion of a task

a black-backed wagtail (Motacilla alba lugens)

pretty, beautiful

being fast asleep, dead to the world when sleeping / pretending to know everything, a know-it-all manner

Alternative form of 白河夜船 (shirakawa yofune)

a fish

(archaic or dialectal) a fish

a fish, especially when used as food / a side dish, specifically referring to fish