Idioms about fish.

there's something fishy about this : means something doubtful or something which is suspected.

 

A big fish in a small pond: when we say that someone is important or powerful but in a small organization. 

 

A fish out of water: someone who is uncomfortable in a particular situation. unhappy person.

a cold fish: a person who does not seem very friendly and does not show their emotions He isn't very demonstrative, but his mother