A hammerhead shark has a wide head shaped like a hammer, called the cephalofoil, with its eyes at the two ends of the head, and a great hammerhead's head width is less than 40% of its total length.

The great hammerhead is the biggest kind of hammerhead shark, and it can grow to 6 m long but rarely exceeds 4.5 m.

Hammerhead sharks live in warm seas around the world, and a great hammerhead lives close to the shore and also far out at sea.

Some scientists once suggested that hammerhead eyes are so far apart that their visual fields could not overlap, but others argued that the wide spacing of the eyes actually improves a hammerhead's binocular vision.

In a 2009 study the winghead shark, a hammerhead, had a 48-degree arc in front of it covered by both eyes, and because a hammerhead's eyes are widely spaced, there is a larger blind area just in front of its snout.

A National Science Foundation grant calls the function of the hammerhead's widened head unclear, with hypotheses that include greater maneuverability and lift. A 2002 study reported that hammerheads show a greater propensity for executing sharp turns and maintain a higher speed through the turn, and suggested that the head gives a greater lateral search area, which may increase the probability of prey encounter.

In one study the hammerhead's head was held level during straight swimming and turning, which its authors said contradicted the maneuverability hypothesis.

A computer simulation study concluded that the hammer head provides greater maneuverability that may be important in prey capture, and the same study found that the head does not provide significant dynamic lift when held parallel to the flow.

Electroreceptors on the underside of a scalloped hammerhead's snout and hammer help it detect buried prey and navigate, and one study reported that the cephalofoil is a better electrosensory detector of hidden prey than a conventional head, sweeping a broad area with no loss in sensitivity.

A study of great hammerheads in the western North Atlantic used satellite tags. Two of the tagged great hammerheads were confirmed pregnant, and one tagged shark migrated from the Bahamas to South Carolina.

In one study, acoustic receivers at oceanic islands detected tagged scalloped hammerheads mostly during daytime hours, and the hammerhead sharks living at those islands could travel more than 40 km on their nightly excursions.

Adult scalloped hammerheads dive rapidly and repeatedly from warm surface waters to depths exceeding 800 meters, where the water is as cold as 5 degrees C, and biologgers on adult scalloped hammerheads showed that muscle stayed warm throughout the deepest part of each dive, while modeling suggested that during deep dives a scalloped hammerhead probably stops heat loss at the gills by suppressing gill function.

As of November 2026, the IUCN Red List lists the scalloped hammerhead as Critically Endangered, and an Australian conservation group says scalloped hammerhead populations in Australia have declined by up to 80%.

A mother hammerhead gives birth to live pups, and a mother scalloped hammerhead carries her pups for 9 to 10 months before they are born, while young scalloped hammerheads swim together in large schools.

Scalloped hammerheads migrate with the seasons, and some travel in large schools heading north for the summer, while Pacific scalloped hammerheads are able to follow geological fault lines along the ocean floor.

Words to know

• binocular: using both eyes
• simulation: computer model
• lift: an upward push
• electroreceptors: electric sensors
• suppressing: holding down