There are many species of catfish, and different species are distributed in different waters. Most catfish live in fresh water. Because of their strong adaptability and low requirements for the environment, catfish are found in rivers, lakes, ponds and streams in many areas. Freshwater catfish is a kind of fish with wide distribution range. However, some catfish live in the sea. For example, sea catfish with thick lips and sea catfish all live in seawater, which are also collectively referred to as sea catfish. These kinds of catfish belong to marine fish.

Catfish in fresh water can't live in seawater, because the environment of seawater and fresh water is quite different. First, the salt content of fresh water is low, while the salt content of seawater is relatively high. If freshwater catfish are put into seawater, they are likely to dehydrate and die. Secondly, the density of seawater is higher than that of fresh water, and the pressure on fish will be greater, so catfish in fresh water cannot live in seawater. Of course, some sea catfish can be put in seawater. Because they live in the ocean themselves, they have completely adapted to the sea environment. It's just that there are few kinds of catfish living in seawater, and they are not very common.