fish in troubled waters

big fish

An important person.

big fish in a small pond

One who has achieved a high rank or is highly esteemed, but only in a small, relatively unimportant, or little known location or organization.

bigger fish to fry

A much more pressing issue to attend to.

bridge over troubled waters

Someone or something that provides support, comfort, and a means to overcome difficult times.

cast one's bread upon the waters

To perform a kind deed or favor without the motivation of any immediate reward or benefit to oneself, though with the possibility of eventual future return.

cold fish

A heartless individual; a person lacking empathy and emotion.

fish or cut bait

To make a decision, especially after a period of delay; to either take action now or forgo the opportunity.

fish out

To search for by rummaging, and then extract (an item from e.g. a container); to obtain.