Hammerhead Shark at Sunset

A male great hammerhead shark swims just below the surface of the water in the Bahamas at sunset.
(© Brian Skerry,

A male great hammerhead shark swims in the Bahamas at sunset. Scientists debate the purpose behind these sharks' hammer-shaped heads. A commonly accepted theory is that the shape allows the shark to scan a wider area of the ocean through its sensory organs. Of the eight species of hammerheads, the great hammerhead shark (Sphyrna mokarran) is the largest, reaching a maximum length of 20 feet. Hammerheads are highly sought after for their fins, suffer a very high mortality rate from bycatch, and reproduce only every two years. As a result, the International Union for the Conservation of Nature lists the great hammerhead's status as "Endangered." Learn more about sharks at our overview page.

For nearly 30 years, photojournalist Brian Skerry has been swimming with and photographing sharks, including great whites, tigers, bulls, blacktips, and great hammerheads all over the world. In a blog post for the Smithsonian Ocean Portal, "Swimming with Sharks," Skerry reflects on these exhilarating experiences.