A fish, in general, lives in water environments. The term "poisson" is French for "fish." **Fish** are **aquatic** animals, meaning they live in water. The **sea** (translated as "la mer" in French) is a large body of saltwater that is home to various types of fish and marine life. On the other hand:
Le désert refers to the desert, which is a dry, arid land area with very limited water sources, unsuitable for fish.
Le ciel means the sky, where birds and aircraft move, but not fish.
Le champ signifies a field, typically used for growing crops or grazing animals, not a place where fish live.