How long will a salt water fish live in fresh water?

A salt water fish will not survive in fresh water for very long. Saltwater fish have adapted to living in a high salt concentration environment. When a saltwater fish is placed in fresh water, its body will start to absorb water and swell up, eventually leading to its death. The exact amount of time it takes for a saltwater fish to die in fresh water will vary depending on the species of fish and the size of the fish. Some fish may die within hours, while others may survive for a few days or even weeks.