The degree of adaptation of fish varies depending on the species. Some marine fish enter freshwater areas to spawn and reproduce, such as eels, which can move near river estuaries, can also tolerate changes in freshwater and seawater. called soda fish, such as goldfish and pufferfish; there are also some that have been tested and proven to be capable of living in fresh water, such as the tongue sole mentioned above. If you have such a status advantage, you can. also do an experiment yourself first!
Almost all hard-shelled marine organisms, such as shrimp and crabs, can survive in fresh water.