Similan Islands Dive Guide — Thailand's Premier Marine Park

The Similan Islands number 1 through 9, running roughly north-south. Each island has distinct dive sites on its east (sheltered) and west (exposed) sides.

Island 9 (Koh Bangu) — Christmas Point: A tumble of granite boulders on the northwest tip creating spectacular swim-throughs at 12–30 meters. Soft coral gardens in the overhangs. Best in light current for dramatic photo compositions.

Island 8 (Koh Similan) — Elephant Head Rock: The signature Similan dive. Enormous granite boulders form a maze of channels, archways, and tunnels from 5 to 30 meters. Navigation requires good buoyancy and spatial awareness. The topography alone makes this one of Asia's most memorable dives.

Island 7 (Koh Payu) — Deep Six & West of Eden: Two sites on opposite sides. West of Eden is a gentle east-side slope with excellent hard coral coverage and anemone gardens — perfect for relaxed diving. Deep Six on the west side has boulders and swim-throughs with better marine life density.

Islands 4–6: East-side sites with hard coral gardens at 5–20 meters — standard for more relaxed dives and night dives. Turtle encounters are common. These sites are the ones reachable on day trips from Khao Lak.

Koh Bon: A separate island north of the main Similan group. The primary attraction is the manta ray cleaning station on the east side at 18–25 meters. From January to April, manta rays visit with high regularity — some days featuring 3–5 different individuals. The west side has a wall dropping to 40+ meters with reef sharks and schools of trevally. Koh Bon is included on most multi-night liveaboard itineraries but not on day trips.

Koh Tachai: Formerly a popular stop, now with restricted access. The site features a long granite ridge with excellent fish life density, including large schools of barracuda and occasional mantas.

Park rules: National park fees (500 THB for foreigners) are included in liveaboard and day trip prices. Gloves are prohibited. No collecting of any marine life. Drone regulations apply above water. Some islands have restricted beach access.

The Similans offer something for every level. East-side sites suit Open Water divers and beginners. West-side boulder sites suit Advanced divers with good buoyancy. Koh Bon is for those seeking manta encounters. The overall experience — clean water, healthy reefs, granite topography — makes a Similan liveaboard one of the best value diving trips in the world.

November 1 – May 15 (official park dates). Peak conditions: January–April. Manta season at Koh Bon: January–April (highest concentration February–March). Visibility typically 15–25m, occasionally reaching 30m. Early season (November–December) offers good diving with fewer boats.