Where can I dive with hammerhead sharks?

Yonaguni Island in Okinawa is Japan's best-documented site, with winter schools off points like Irizaki. Mikomoto Island near Tokyo is a warmer-water alternative in summer.

When is hammerhead season?

At Yonaguni the core window is December to March, tied to winter water of roughly 21–25°C. Mikomoto runs the opposite way, best June to October.

Are hammerhead sharks dangerous?

Scalloped hammerheads are not considered dangerous to divers. They eat fish, rays and cephalopods, and they are skittish — the usual problem is that they keep their distance, not that they come close. The International Shark Attack File records no confirmed fatal attacks by hammerhead species.

Animal profile

Where to see hammerhead sharks

Sphyrna lewini (scalloped hammerhead)

A scalloped hammerhead shark passing close to the camera, the notched front edge of its wide head clearly visible, with a second shark behind it. — Hammerhead Shark, photographed at Cocos Island, Costa Rica. Photo by Barry Peters · CC BY 2.0

The scalloped hammerhead is named for the notched front edge of its wide, flattened head — a structure called a cephalofoil that spreads its electro-sensory organs and nostrils over a larger area for better prey detection, and gives it enhanced binocular vision. The species forms large schools, sometimes numbering in the hundreds, a behaviour thought to reduce individual swimming effort and offer younger sharks protection. Scalloped hammerheads grow slowly and mature late, which makes them acutely vulnerable to fishing; the IUCN uplisted them to Critically Endangered in 2019, citing an estimated decline of at least 80% over three generations, driven mainly by the fin trade.

Size: 3–4 m
Diet: Fish, rays and cephalopods

Best places to see hammerhead sharks

Japan · Yonaguni Island, Okinawa High confidence

Well documented, and reliably seen in season.

Best time: Winter, December to March

Galápagos · Darwin & Wolf Islands, plus Gordon Rocks High confidence

Well documented, and reliably seen in season.

Best time: June to October, the cool garúa season

How to identify a hammerhead shark

Wide, flattened head with a scalloped (notched) front margin — that notch separates this species from other hammerheads.
Grey to grey-brown back with a pale underside, and a tall, slightly curved first dorsal fin.
Usually seen in large, tightly packed schools rather than alone, over deep drop-offs and current-swept points.

Meeting them responsibly

Keep your breathing quiet and your movements slow — hammerheads are skittish and bubble noise pushes a school away.
Never chase or swim toward a school. Hold your depth and let them pass on their own terms.
Hold your buoyancy off the rock at current-exposed sites; it is easy to crash into the reef while looking up at sharks.

Frequently asked questions

Where can I dive with hammerhead sharks?: Yonaguni Island in Okinawa is Japan's best-documented site, with winter schools off points like Irizaki. Mikomoto Island near Tokyo is a warmer-water alternative in summer.
When is hammerhead season?: At Yonaguni the core window is December to March, tied to winter water of roughly 21–25°C. Mikomoto runs the opposite way, best June to October.
Are hammerhead sharks dangerous?: Scalloped hammerheads are not considered dangerous to divers. They eat fish, rays and cephalopods, and they are skittish — the usual problem is that they keep their distance, not that they come close. The International Shark Attack File records no confirmed fatal attacks by hammerhead species.