Unlike most sharks, the Bull Shark (Carcharhinus leucas) can tolerate fresh and brackish water. They have even been found hundreds of miles up river. Many speculate that the sharks do this to find a more bountiful supply of food or to even give birth. The juvenile sharks may face fewer predators or have a greater access to food sources in freshwater system. This makes the Bull Shark a very dangerous predator and people have been attacked while swimming in rivers.