“Fish out of water” means feeling awkward, uncomfortable, or out of place because you are in a situation that is unfamiliar to you.
The image behind the idiom is very direct. A fish can live naturally in water, but out of water it struggles and cannot function normally. That picture helps explain why the phrase is used for people who suddenly find themselves in an environment where they do not know the rules, the culture, or what to do next.
You will often hear it when someone is new to a job, school, social group, or city.
- I felt like a fish out of water at my first law conference.
- He was a fish out of water when he joined a team of experienced dancers.
The phrase is usually not literal. It is a figurative way to say, I do not belong here yet or I am not comfortable here. It can describe a brief moment of discomfort or a longer period of adjustment.
This idiom is useful because it expresses both unfamiliarity and visible discomfort in one short image.