After tagging more than 75 sharks, researchers at the University of Miami have built a database that tracks the movements of several species. The nine individuals here have vastly different migration patterns. The bull shark Lia covered only 20 miles over 74 days, while Linda, a tiger shark, traveled more than 2,000 miles up the Eastern seaboard. "She encircles an area the size of a billion football fields," says Hammerschlag. "I had no idea we would see that scale."