The Bull Shark (Carcharhinus leucas) is a species of shark found in both fresh and salt water worldwide. While it spends most of its life in the ocean, it is capable of swimming in freshwater for long periods of time. This is due to a "salt exchange system", which prevents too much salt from leaving its blood cells, which would kill most other sharks. Its name comes from its stocky appearance and its behavior of charging into its prey like a bull.
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