Koh Tachai Pinnacle, Thailand: Currents and Pelagic Encounters

Koh Tachai Pinnacle sits as a substantial submerged reef south of the main island, accessible only by dive boats. The site’s defining feature is its large dome-shaped pinnacle, rising from deeper waters with its apex at 12 metres. This main structure is complemented by a smaller pinnacle, connected by a sandy stretch, forming a complex topography that provides varied habitats and challenges depending on your approach.

The southern section of the main pinnacle showcases the deeper profile, dropping to 40 metres and beyond. Here, the dome transition into deeper areas with large rock formations. Divers will find passages and overhangs along the western side, offering shelter and exploration opportunities within the rock gardens and providing a dynamic environment where water movement dictates exploration patterns.

On the eastern flank of the pinnacle, the landscape shifts to stacks of smaller rocks, extensively covered in hard corals and gorgonian fans. This area, particularly the northern face, is characterised by soft corals, creating walls of colour that thrive in the current-rich environment. The vibrant marine growth here is a clear indicator of consistent water flow, bringing nutrients that support this robust ecosystem.

Koh Tachai Pinnacle is known for its strong, often unpredictable currents, which are a defining characteristic of the dive. These currents, while demanding, are responsible for the site’s nickname, 'fish soup', as they draw in a remarkable abundance of pelagic life. You'll often find yourself holding onto the reef, watching the action unfold, rather than actively swimming against the flow.

The site regularly hosts reef sharks (Carcharhinus amblyrhynchos) and leopard sharks (Stegostoma tigrinum), which are often seen cruising the deeper sections and sandy bottoms. Beyond these resident sharks, the strong currents make Koh Tachai a key aggregation point for larger pelagics. Seasonal visitors like manta rays (Mobula birostris) and whale sharks (Rhincodon typus) are drawn to the rich feeding grounds here, often providing open-water encounters.

In addition to the larger species, the site is teeming with schooling fish. You will encounter Blue Fin Trevally (Caranx melampygus), various Jacks, Mackerel, and Tuna (Thunnus spp.) swimming in coordinated patterns. Closer to the reef, Clown Triggerfish (Balistoides conspicillum), Parrotfish (Scaridae family), and Barracuda (Sphyraenidae family), including Pickhandle Barracuda (Sphyraena jello) and Great Barracuda (Sphyraena barracuda), forage and hunt.