The powder‑white island that stayed closed for years to protect its fragile beauty

The northern paradise that stayed closed for years to protect its beauty

the island of powder‑white sand, turquoise shallows, and deep‑blue ocean energy

Koh 11 — known as Koh Tachai and pronounced locally as koh tà‑chai (เกาะตาชัย, soft “tà,” smooth “chai”) — is the northern jewel of the Similan–Surin region. It’s famous for its powder‑white beach, glowing turquoise water, and deep‑ocean dive sites where manta rays and whale sharks sometimes appear. Koh Tachai is breathtaking, but also fragile — so fragile that Thailand closed the island for many years to let nature recover.

“Koh 11 is the island that glows softly on the sand and wildly in the deep.”

The first impression of Koh 11

Koh Tachai looks like a dream — a long curve of white sand, bright turquoise water, and a quiet forest line that feels untouched. Boats approach slowly because the water is so clear you can see the sand ripples beneath the surface. The island feels bigger, brighter, and more open than the southern Similans.

Pam always says, “Koh Tachai is the island that glows even on a cloudy day.”

The mood of Koh 11

Koh 11 has two distinct moods:

• soft and gentle on the beach
• deep and powerful in the open water

Expect:

• powder‑white sand
• bright turquoise shallows
• deep‑blue drop‑offs
• peaceful forest
• open‑ocean energy

“Koh Tachai feels like two worlds living side by side.”

The beach — soft, bright, and unforgettable

Koh Tachai’s beach is one of the most beautiful in the Andaman Sea. The sand is fine and white, the water is clear and glowing, and the shoreline feels peaceful and wide.

Visitors love:

• the softness of the sand
• the bright, shallow turquoise
• the quiet forest behind the beach
• the feeling of space and calm

It’s the kind of beach that makes you slow down without trying.

The underwater world — deep, rich, and full of life

Koh 11 is famous for its deep‑water dive sites, especially around Tachai Pinnacle. This is where the open ocean meets the reef, creating a powerful, nutrient‑rich environment.

Divers often see:

• manta rays
• whale sharks (seasonal)
• schools of barracuda
• trevally hunting in the blue
• colorful reef fish
• dramatic granite formations underwater

The currents can be strong, which is why Koh Tachai is loved by experienced divers.

“Tachai Pinnacle is where divers go to feel alive.”

Closed for many years — a fragile paradise protected

Koh Tachai became so popular that the ecosystem started to suffer. To protect the coral, the beach, and the marine life, Thailand made a rare and bold decision:
Koh Tachai was closed for many years.

During the closure:

• no visitors were allowed
• no boats could land
• no beach access
• no diving or snorkeling around the island
• the forest and sand were left completely untouched

This long closure allowed the island to recover naturally — the sand became soft again, the coral began to heal, and marine life returned in larger numbers.

Koh Tachai is still managed with strict protection today, with controlled access and no overnight stays.

Above the water — colors, calm, and open sea

From the boat, Koh 11 looks like a perfect tropical island:

• white sand glowing in the sun
• turquoise water shifting into deep blue
• forest moving softly in the wind
• open ocean stretching endlessly north

It feels like the final bright chapter before the Andaman Sea becomes deep and wild.

Why people love Koh 11

• powder‑white sand
• glowing turquoise water
• manta‑ray and whale‑shark potential
• dramatic deep‑water dive sites
• peaceful, wide beach
• a perfect mix of calm and adventure
• a rare island that was protected by closing it completely

Koh 11 is the northern paradise of the Similan–Surin region — the island that stayed closed so it could stay beautiful.