Reaching over 13ft in length and weighing up to 700lbs, the bull shark is one badass freshwater monster. However, bull sharks are not naturally found in freshwater. They have been documented to swim as far as 2,500 miles upriver into freshwater systems. This is often due to the flooding of smaller bodies of water near deltas and estuaries, making paths from one river or lake to another for a short period of time. After the sharks swim far enough upstream, some of these paths evaporate, making it impossible for them to return to sea; therefore, the freshwater systems in which they become entrapped become their new homes.