Scalloped Hammerhead

What to look for

Identify them by their wide head. This shape is called a cephalofoil. Most adults reach 2-3 m in length. They are often dark grey on top. The underside is usually white.

Look for the distinct silhouette. You will see them against the blue background because their dark bodies contrast with the light. I first saw a large school in 2014 near the Andaman Sea. They move with steady, rhythmic tail beats.

Behaviour you’ll observe

These sharks often travel in schools. You might see 20 to 50 individuals at once. They prefer open water or reef edges. They usually stay in the upper water column during the day.

They are highly active swimmers. Most hammerheads must keep moving to breathe. This constant motion makes them easier to spot than resting reef sharks. You will rarely see them hunting in large groups.

Where and when

Timing is everything for these sightings. The best months are March, April, May, and June. During this window, the water clarity improves significantly. Sighting probability is roughly 1 in 12 dives at peak season.

In Thailand, Richelieu Rock is a top location. You should aim for dives between 25 m and 30 m deep. I found a group of 30 sharks there in May 2017. The current can be strong here.

In Indonesia, try Manta Point Nusa Penida. The sharks often appear when the currents are moderate. They tend to congregate near steep drop-offs. You may need to drift with the current to see them.

If you visit Komodo, look near the northern islands. The deep channels attract many larger predators. Always check the seasonal weather reports before booking.

Diver etiquette

Keep a respectful distance. Do not chase the animals. They are sensitive to sudden movements. Stay low in the water column.

Avoid touching the sharks. This is for their safety and yours. A single touch can disrupt their natural behavior. If you see a school, stay still. Let them come to you instead of swimming toward them.

Watch your buoyancy closely. Do not kick up silt or sand. This obscures visibility for everyone in the group.

Conservation status

The IUCN Red List classifies this species as Critically Endangered. This is due to heavy fishing pressure globally. Many sharks are caught for their fins.

Local protections help a little. Some marine parks in Southeast Asia restrict fishing. However, illegal fishing remains a massive problem in remote areas. We must support sustainable dive operators.

Danger level

The danger level is low. They are not aggressive toward divers. Most incidents involve accidental contact rather than attacks.

Keep your hands inside your body. Do not wave your arms around. If a shark approaches, stay calm. Panic often triggers more curiosity from the animal.