Shark Fin Reef (Hin Pae): Similan Islands' granite ridge

Shark Fin Reef, or Hin Pae, takes its name from the elongated granite ridge that breaks the surface in a series of peaks resembling a shark's fin. This formation, extending south and east from Similan Island #3 (Koh Payan), covers a significant distance and creates a varied underwater landscape. You'll find walls, plateaus, fissures, and small caves carved into the rock, with other smaller boulders scattered down to deeper sandy areas at 40 meters.

The dive often begins with the northern and eastern sides, presenting a more gradual sloping reef that transitions into sand at depth. As you move towards the southwest, the topography shifts dramatically to a steeper descent. Here, large, pillar-like hexagonal rock formations dominate the landscape, forming dramatic structures that invite exploration. This area offers a distinct feel, with crevices and overhangs providing shelter for smaller reef inhabitants, while the deeper sections open up to sandy flats where larger pelagics sometimes patrol.

A notable feature on the southeastern end of these impressive hexagonal formations is a large, natural passage. This offers a clear swim-through that leads you across to the opposing side of the reef. Navigating this passage gives you a unique perspective on the reef's structure and often serves as a natural current break or a path for marine life moving between sections of the site. It is also an excellent vantage point to observe passing species in the blue.

The marine life at Shark Fin Reef is diverse, reflecting both its reef structure and exposure to open water. You'll regularly encounter leopard sharks (Stegostoma tigrinum) resting on the sandy bottom, particularly in the deeper, more sheltered areas. White-tip reef sharks (Triaenodon obesus) are also present, often patrolling the reef edges. Look out for the humphead parrotfish (Bolbometopon muricatum), which can be seen grazing on corals, along with napoleon wrasse (Cheilinus undulatus) a common sight around the major rock formations.

Beyond the sharks and large reef fish, the site supports a healthy population of smaller reef dwellers. Marble stingrays (Taeniura lymma) and pink whiprays (Himantura fai) are often found in the sandy areas adjoining the main reef. Expect to see moray eels (Muraenidae) tucked into rock crevices, lionfish (Pterois volitans) hovering in sheltered spots, and scorpionfish (Scorpaenidae) camouflaged on the rocks. While not the primary focus, the site's shallow platforms and coral bommies are home to an array of macro life, including various nudibranchs and flatworms which thrive in clearer waters.

One of the distinguishing features of Shark Fin Reef is its exposure and the potential for moderate to strong currents. While there are protected zones, especially along the extensive granite ridge, understanding the current patterns is key to planning your dive. These currents often bring in nutrients and pelagic visitors, adding another layer to the diving experience. The wide visibility, which can extend up to 30 meters, allows you to appreciate the scale of the site and spot marine life from a distance.

The site's expansive nature, with its combination of dramatic granite formations, sandy slopes, and a well-defined underwater passage, offers a complete dive experience. From the shallow reef tops ideal for photography to the deeper sections frequented by larger species, Shark Fin Reef caters to different interests. Its reputation for resident and passing pelagics, combined with the structural complexity of the reef, makes it a dynamic environment that rarely disappoints.