Similan & Richelieu Rock

The route covers the Similan Islands National Park and three key sites to the north — Koh Bon, Koh Tachai, and Richelieu Rock. This is Thailand’s premier diving route and one of the best in Southeast Asia. The four-night trip includes 14–16 dives, moving from south to north — from the granite boulders of the Similans to the legendary Richelieu pinnacle.

The Similan Islands are nine islands in the Andaman Sea, 70 km from the Khao Lak coast. Underwater — two contrasting landscapes. The western side features massive granite boulders resembling those of the Seychelles, forming canyons, passages, and caves. The boulders are covered with gorgonians and soft corals, with morays and lobsters hiding in crevices. The eastern side offers gentle coral gardens with hard corals where turtles, parrotfish, and schools of fusiliers feed.

Koh Bon is a rocky island with a sheer wall on the western side covered in pastel soft corals. The main reason to stop — manta rays. Peak manta season is January–April, when currents bring plankton to the island wall and rays come to feed. This is one of the most reliable sites for manta encounters in Thailand.

Koh Tachai is an underwater pinnacle in the open sea. The pyramid-shaped rock is covered in large gorgonians and attracts pelagic fish: schools of barracuda, trevally, and batfish. Currents here are strong and unpredictable, making for dynamic dives.

Richelieu Rock is the route’s highlight and one of the world’s best dive sites. A limestone pinnacle a few kilometers from the Surin Islands, completely hidden underwater. Every centimeter of rock is covered in purple soft corals and anemones — the “purple haze.” In the crevices — seahorses, ghost pipefish, harlequin shrimps, frogfish. Whale sharks regularly visit Richelieu — currents carry masses of plankton.

The route concludes with a dive on the Boonsung wreck — a sunken tin mining vessel at 18 meters depth, now an artificial reef with excellent macro: ghost pipefish, cuttlefish, seahorses. Season is November–May, the park is closed the rest of the year. Visibility 15–30 meters, water 27–29°C.