Art illustration - Bull Shark - Oceans & freshwater - (Carcharhinus leucas) Is a species of one of the few sharks that draws the estuaries to reach fresh water. It can measure up to 3.4 m in length. It feeds on all kinds of animals, including other sharks. It can be dangerous for the human being. The ability of this shark to enter fresh water is thanks to a special gland they have in the kidney that allows them to contain salt water in their body and expel fresh water.