Hammerhead sharks can be recognized by their flattened, rectangular-shaped heads suggesting a hammer. The nostrils, as well as the eyes, are located on the outer edges of the head. As the hammerhead swims, it swings its head back and forth through the water, possibly increasing the chances of detecting food. These sharks are found in tropical and suptropical waters of all oceans, and the favorite food of some species includes stingrays. The common thresher shark , Alopias vulpinus , is easily recognized by the elongated top lobe of its tail fin.
All thresher sharks have tail fins nearly as long as the rest of the body.
They have gray topsides and white undersides. Threshers are found in the warm and subtropical waters of the Atlantic and Pacific Oceans, often feeding in groups on schools of small fish. These sharks thresh their prey, that is, they use their tail fins to stun and scare fish into a group that can be fed upon more easily. The whale shark and basking shark , Cetorhinus maximus , have an unusual feeding method. These two species, along with the recently discovered megamouth , Megachasma pelagios , are specially adapted for filtering large numbers of small organisms out of the water.