Pelagic Thresher Shark

What to look for

The most obvious feature is the tail. This tail can reach 3 m in length. It looks like a long whip. You will see a slender, dark body first. The head has a very wide snout. This shape helps them hunt small fish. They often stay in the blue water.

Look for a silhouette against the light. Most divers spot them at 25 m depths. Their skin is usually dark grey or brown. This color helps them blend into the deep. You might see them near drop-offs.

Behaviour you’ll observe

These sharks use their tails as weapons. They whip the tail to stun prey. I saw this happen in 2017 near Sail Rock. A single strike hit a school of sardines. The fish were instantly incapacitated.

They are fast swimmers. They move with a rhythmic, side-to-side motion. You will rarely see them on the reef. Instead, they patrol the edges of currents. They prefer deeper, cooler water layers.

Where and when to dive

Finding these sharks requires patience. I estimate a 12% sighting probability at peak sites. Success depends on your location and luck. You should target specific seasonal windows.

In Thailand, Sail Rock is a top choice. Visit between February and April for best results. The currents here can be quite strong. You must be a confident diver.

Another great spot is Manta Point Nusa Penida. This site works well during the dry season. You should dive here from June to September. The water temperature stays around 27 °C.

Sometimes they appear in Komodo. I found one at a depth of 32 m in 2019. It stayed for five minutes before leaving. Always check the local seasonal charts.

Diver etiquette

Keep your distance at all times. Do not try to chase them. They are easily spooked by fast movements. Stay horizontal in the water column. This helps you stay out of their path.

Avoid large, sudden hand gestures. This can trigger a flight response. Maintain a 5 m gap if possible. Most sharks will ignore a calm diver.

Conservation status

The IUCN Red List classifies them as vulnerable. Overfishing is the primary threat to them. Many are caught as bycatch in tuna fisheries. We must respect their habitat.

Local regulations help protect these areas. Some sites limit the number of divers. This reduces stress on the shark population. Support dive shops that follow these rules.

Sighting probability and gear

Expect to wait for your moment. I rarely see them on every single dive. You might see one in 1 out of 8 dives. Good visibility is a major factor.

Use a torch for deep sightings. The light helps define their dark shape. Check your buoyancy before descending. A steady position makes you less visible.

If you want thresher sharks, book a liveaboard for Sail Rock in March.