Bull sharks live throughout the world, in shallow, warm ocean waters. They've been known to swim up into freshwater rivers. Humans are not part of a bull shark's normal prey. Bull sharks will eat almost anything, but their diet consists mainly of fish. They also sometimes eat dolphins and sea turtles. Bull sharks even eat other sharks. They hunt during the day and at night.

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Sharks must keep salt in their bodies to survive, and most can live only in salt water. But bull sharks have developed special adaptations—the way their kidneys function and special glands near their tails—that help them keep salt in their bodies even when they're in freshwater. Scientists are still studying these sharks to figure out why they developed this unusual ability.