Which sharks can swim far up freshwater rivers?

While most sharks are marine animals, some species are capable of entering or residing in freshwater environments. The most notable of these is the bull shark (Carcharhinus leucas), which is famous for its ability to travel vast distances up rivers. Bull sharks have been documented nearly 3,700 km (about 2,300 miles) up the Amazon River and hundreds of kilometers up Africa’s Zambezi River, as well as in Lake Nicaragua.123

Another species that frequents freshwater habitats is the Ganges shark, which is primarily found in the Hooghly River in India, as well as in other tropical freshwater and brackish estuaries. These sharks, often referred to as river sharks, possess physiological adaptations that allow them to manage osmotic balance in low-salinity environments, such as lowering the concentration of urea in their blood.456