Are Hammerhead Sharks Dangerous? Real Risk to Swimmers

What the shark bite records show

The International Shark Attack File (ISAF) at the Florida Museum of Natural History is the world’s main database of shark bites, with cases going back to the 1500s. It counts as “unprovoked” any bite on a live person in the shark’s natural habitat when the person did nothing to provoke the shark. Its table of species confirmed in unprovoked bites includes:

Unlike gray requiem sharks, which are hard to tell apart, hammerheads are almost always identified correctly. The ISAF notes that bites by easily recognized sharks such as white, tiger, sand tiger, hammerhead and nurse sharks nearly always name the right species. So the low hammerhead total is probably close to the truth, not the result of missing records. The bull shark is a different story, as explained in Are bull sharks the most dangerous shark?

For scale, the ISAF confirmed 65 unprovoked shark bites worldwide in 2025 from all species, nine of them fatal. More on overall risk is in How often do sharks attack humans?

Which hammerheads could hurt a person?

There are about ten hammerhead species, and most are too small to be a real threat. The bonnethead, a common small hammerhead of Florida and the Gulf of Mexico, is usually only 80–90 cm (2.6–3 ft) long and feeds mainly on crabs, shrimp and small fish.

The ISAF points out that almost any shark around 1.8 m (6 ft) long or more could injure a person, whether or not it means to feed. Among hammerheads, that applies mainly to the larger species: the scalloped hammerhead, which reaches about 4 m (13 ft), the smooth hammerhead, up to about 5 m (16 ft), and the great hammerhead, the biggest of all at up to about 6 m (20 ft).

The great hammerhead is the one most often described as potentially dangerous. It is very large, has triangular, strongly serrated teeth, and is an active predator that eats other sharks. Even so, very few bites have been pinned on this species specifically, and the Florida Museum’s advice is simply to treat it with caution and respect.

How great hammerheads behave around divers

Divers who meet great hammerheads usually describe them as shy, wary or uninterested. A great hammerhead may circle once or twice to look at a diver and then swim off. Some approach closely, and a few have been reported to make sudden close passes, especially when divers first enter the water.

At popular dive sites such as Bimini and Tiger Beach in the Bahamas, operators use bait to bring great hammerheads close to divers, mainly in the cooler months. Under these conditions the sharks can swim within arm’s length. Baiting changes natural behavior and keeps excited sharks close to people, and scientists and divers still debate its effects.

Like other sharks, a great hammerhead that feels threatened may give warning signals, such as swimming stiffly or jerkily with its pectoral fins lowered. That is a clear sign to back away.

Why hammerheads bite people so rarely

Hammerheads are specialists. They hunt mainly bony fish, rays, crabs, squid and octopus, often close to the seabed, and the great hammerhead is famous for pinning stingrays to the bottom with its head. Their mouths are relatively small for their size, tucked under the wide head. People are simply not part of their diet.

Schools of scalloped hammerheads, which gather by the hundreds at places such as the Galapagos Islands and Cocos Island in Costa Rica, are often wary of divers. Many divers find that the sharks keep their distance from the noise and bubbles of scuba gear.

People are far more dangerous to hammerheads

The real danger runs the other way. Hammerheads are among the most threatened sharks in the world because they are caught for their large, valuable fins and die easily on fishing lines. The IUCN lists the great and scalloped hammerheads as Critically Endangered and the smooth hammerhead as Vulnerable. The great hammerhead is estimated to have declined by more than 80% in about 70 years, as explained in Why are great hammerheads Critically Endangered?

Each year people kill millions of sharks, including many hammerheads, while no hammerhead has ever been confirmed to have killed a person. The global toll is explained in How many sharks are killed each year?

Staying safe around hammerheads

Hammerheads are wild predators, and a few simple habits keep encounters safe for both people and sharks:

• Watch hammerheads from a distance and never touch, chase, corner or feed them.
• Dive with experienced local guides at known hammerhead sites and follow their briefings.
• Avoid swimming near people who are fishing, near fish-cleaning areas, or in murky water at dawn and dusk, when many sharks feed.
• Calmly leave the water if a shark swims stiffly, lowers its pectoral fins or keeps returning.

Anyone bitten by a shark needs emergency medical help immediately: call 911 (US), 112 (EU) or 999 (UK). Local shark species and beach safety are covered in sharks in Florida.