A firsthand account of a North Andaman liveaboard diving cruise exploring the Similan Islands, Koh Bon, Koh Tachai, and Richelieu Rock — widely considered the best scuba diving in Thailand. In March 2026, I joined a North Andaman liveaboard diving expedition in Thailand aboard the Mandarin Queen 9, departing from Phuket to explore the country’s most legendary sites in the Andaman Sea. This region — encompassing the Similan Islands, Koh Bon, Koh Tachai, the Surin Islands, and Richelieu Rock — is widely regarded as the best diving area in Thailand and one of the premier liveaboard destinations in Southeast Asia.

Above the surface, the scenery is already spectacular: powder-white beaches, massive granite boulders sculpted by time, and water in surreal shades of turquoise and deep blue. But it is underwater that North Andaman diving truly shines, with enormous fish schools, pristine coral reefs, frequent pelagic encounters, and exceptional macro life.

Our route followed the classic Similan Islands liveaboard itinerary, gradually moving north through increasingly remote sites before culminating at Richelieu Rock — often ranked among the best dive sites not only in Thailand but in the world.

📍 North Andaman Liveaboard Itinerary Overview

A North Andaman liveaboard is the ultimate way to explore Thailand’s most remote and spectacular dive sites, far beyond the reach of day boats. These cruises combine world-class underwater scenery with the convenience of living aboard a fully equipped dive vessel.

Typical duration

Most itineraries last 4 to 7 days, offering between 12 and 20 dives, including early-morning, sunset, and sometimes night dives. Longer trips allow more time at flagship sites such as Richelieu Rock.

Departure point

Liveaboards usually depart from Thap Lamu Pier, north of Phuket. Transfers from Phuket hotels or the airport are typically arranged by the operator on embarkation day.

Dive sites covered

A classic North Andaman route includes the region’s highlights:

• Similan Islands — dramatic granite boulders, swim-throughs, and vibrant reefs
• Elephant Head Rock & Christmas Point — iconic topography and schooling fish
• Koh Bon — manta ray cleaning station and pelagic territory
• Koh Tachai Pinnacle — powerful currents and dense fish aggregations
• Surin Islands & Richelieu Rock — Thailand’s most biodiverse site and a whale shark hotspot

Experience level

Most dives are suitable for intermediate to advanced divers. An Advanced Open Water certification and comfort with currents are recommended, particularly for exposed pinnacles and deeper profiles.

Best season

The North Andaman dive season runs from November to April, when seas are calm and visibility is typically excellent. Peak conditions usually occur between January and March, offering the highest chances of manta ray and whale shark encounters.

This combination of remote locations, diverse marine life, and dramatic underwater landscapes makes North Andaman liveaboard diving one of the finest scuba experiences in Thailand.

Day 1 — Departure from Phuket

The adventure began in the late afternoon with a transfer from Phuket to Thap Lamu Pier. Boarding the Mandarin Queen 9 felt like stepping into a floating dive resort — spacious dive deck, comfortable cabins, sun deck, and a professional crew.

After cabin allocation, a comprehensive briefing covered safety procedures, dive protocols, and the itinerary ahead. Dinner was served as the boat quietly departed into the Andaman night, setting course for the Similan Islands.

Falling asleep to the gentle motion of the sea, knowing that world-class diving awaits at dawn, is one of the unique pleasures of liveaboard travel.

Day 2 — Similan Islands: Granite Landscapes

The first full day delivered four dives in the Similan Islands, each showcasing different underwater terrain.

• Three Trees offered gentle conditions, coral bommies, and abundant reef life — a perfect warm-up dive.
• Nam Chai is a mix of sand patches and scattered reefs, ideal for spotting rare macro life. We were lucky to encounter two ornate ghost pipefish, an unforgettable highlight so early in the trip.
• Christmas Point featured dramatic swim-throughs and rocky outcrops teeming with fish. At one point, around 20 meters deep, the route passes beneath a trapped air pocket inside the granite formations.
• North Point revealed sloping reefs and scattered granite formations.

Day 3 — Elephant Head Rock, Koh Bon and Tachai Pinnacle

Day three moved north to increasingly remote and spectacular sites.

Elephant Head Rock is one of the Similans’ most iconic dives — giant boulders stacked underwater, forming tunnels, arches, and swim-throughs. Visibility was excellent, and large trevallies cruised in the blue.

At Koh Bon, we explored a famous manta cleaning station. There was no manta, but the site’s topography — a ridge dropping into the deep blue — screams “pelagic territory.” At one point, we even passed beneath an explosive “sploosh,” a powerful surge wave collapsing from the surface above — a dramatic reminder of the raw energy of the Andaman Sea 😱🤿

Then came two dives at Tachai Pinnacle, a submerged seamount rising from the depths. This site delivered exactly what it’s known for: dense fish schools, including barracuda and trevally swirling in powerful currents. It felt like diving inside a living tornado of fish.

Day 4 — Richelieu Rock: The Crown Jewel

Day four was dedicated entirely to Richelieu Rock, the undisputed highlight of North Andaman diving.

This horseshoe-shaped pinnacle rises from deep water and explodes with life. Soft corals in shades of purple, pink, and red cover the rock, while enormous schools of fish obscure the reef like moving clouds.

Across four dives — including a sunset dive — we experienced:

• Massive bait balls hunted by trevallies
• Dense schools of fusiliers and snappers
• Intricate macro life hidden among the corals

Richelieu Rock is also famous for whale sharks. Although encounters are never guaranteed, every moment underwater carries that electric anticipation: it could appear at any second (but it did not…).

Even without one, the biodiversity here is overwhelming. It’s the kind of site where you don’t know where to look — wide-angle action everywhere, yet macro treasures at every glance.

Day 5 — Final Dives and Return

The final day included three last dives on the return south:

• A second exploration of Tachai Pinnacle.
• Two more dives at Koh Bon, including one on a smaller pinnacle away from the main reef.

After surfacing from the last dive around 3 PM, the journey back to the pier began. Gear was rinsed, logbooks completed, photos exchanged, and that familiar liveaboard melancholy set in — the feeling that something special is ending.

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Marine Life Highlights of the North Andaman

This itinerary showcases the best of Thailand’s underwater biodiversity:

• Vibrant hard and soft coral reefs
• Reef sharks and turtles
• Giant trevally and barracuda schools
• Manta ray territory at Koh Bon
• Extraordinary macro life at Richelieu Rock
• Possibility of whale shark encounters

Water clarity was generally excellent, and reef health appeared strong across most sites.

Life On Board Mandarin Queen 9

The Mandarin Queen 9 functioned as a comfortable and efficient dive platform. Days followed a rhythm familiar to liveaboard divers:

Wake — Dive — Eat — Rest — Dive — Eat — Dive — Eat — Sleep

Meals were plentiful and varied, snacks available between dives, and the crew handled equipment with impressive efficiency. Between dives, the sundeck offered the perfect place to relax, watch sunsets, or simply stare at the endless Andaman horizon.

🌊 Conditions and Difficulty

Diving in the North Andaman Sea is rewarding but can be demanding, especially at exposed offshore pinnacles. Conditions vary significantly from sheltered reef dives to high-energy sites in open water.

Currents

Currents range from mild to strong depending on the site, tide, and moon phase. Sheltered areas in the Similan Islands may offer relaxed conditions, while sites such as Koh Bon and Tachai Pinnacle can experience powerful flow that attracts large pelagic fish. Drift diving skills and good buoyancy control are highly beneficial.

Depth ranges

Most dives take place between 10 and 30 meters (33–100 ft). Shallow reef tops often begin around 5–10 meters, while deeper slopes and pinnacles extend beyond recreational limits. Many highlights — including schooling fish and manta cleaning stations — are typically found in the 18–25 meter range.

Nitrox availability

Nitrox (Enriched Air) is commonly available on liveaboards and strongly recommended. It allows longer bottom times and reduced nitrogen loading, particularly useful on multi-dive days with repetitive deep profiles.

Thermocline possibility

While water temperatures are generally warm (27–30 °C / 81–86 °F), sudden thermoclines can occur, especially at deeper sites and around upwellings that bring nutrient-rich water. Temperatures may briefly drop by several degrees, so a full wetsuit is advisable even in tropical conditions.

Overall, North Andaman diving is best suited to confident divers comfortable with varying conditions, but the rewards — spectacular topography, dense marine life, and potential big-animal encounters — are exceptional.

Important Flying Safety Rule

The final dive ended around 15:00 on the last day. Divers are strongly advised to wait at least 18-24 hours before flying to minimize the risk of decompression sickness.

This is a standard recommendation for multi-day dive trips and should always be factored into travel plans.

Final Thoughts — Heaven Above and Below

North Andaman diving truly feels like a place where “heaven on earth meets heaven underwater.” Few destinations combine such dramatic island scenery with world-class marine life and varied dive topography.

From the granite cathedrals of the Similans to the fish-packed pinnacle of Richelieu Rock, this cruise delivered one unforgettable dive after another.

For anyone seeking the best diving Thailand has to offer — and one of the finest liveaboard experiences in Southeast Asia — the North Andaman should be at the very top of the list.

Frequently Asked Questions — North Andaman Liveaboard Diving