Which shark species is known for its ability to survive in freshwater?

The bull shark is the shark species best known for surviving in freshwater.

Bull sharks (Carcharhinus leucas) are euryhaline, meaning they can regulate their bodies across a wide range of salt concentrations. They commonly move between the sea, estuaries, and rivers, and have even been recorded far upstream. This unusual ability comes from coordinated changes involving the kidneys, gills, liver, and rectal gland, which help control water and salt balance.

The species has been reported in freshwater locations including Lake Nicaragua and the Amazon River. Bull sharks have also traveled roughly 700 miles up the Mississippi River to the area near Alton, Illinois. Their freshwater tolerance is especially important for young sharks, which often use low-salinity nursery habitats for protection from larger marine predators.

A common mix-up is calling the bull shark a “true freshwater shark.” It is not exclusively freshwater; it is a coastal species that can move between freshwater and saltwater. Several river shark species also tolerate freshwater, but the bull shark is the classic answer in general-audience trivia.