Bull sharks have a surprising adaptability: they are able to move freely between salt and fresh water. Tune-in to five full weeks of Sharkfest on National Geographic every night at 8/7c—and available next day on Hulu. | National Geographic

Bull sharks are a unique shark species that can survive in both saltwater and freshwater. They're often found in brackish waters and estuaries. The Investigation Shark Attack team looks at the biology of bull sharks to understand why they might be behind a speight of investigatory bites, which are usually incredibly rare. Watch Investigation Shark Attack on Sundays at 8pm, from July 13th on National Geographic WILD UK. | National Geographic UK