The scalloped hammerhead shark has a distinctive hammer-shaped head, with olive, bronze or brown coloring and white belly. It lives in warm tropical waters off Australia and Central America, ranging in size from 3 to 26 feet. Hammerheads are threatened by overfishing, as about 73 million sharks are killed annually, including 3 million hammerheads targeted for their fins. Their large heads help them detect prey and approaching threats through widely spaced eyes and nostrils.