Island days · Trang archipelago
Koh Mook & the Emerald Cave
Torch-lit darkness, then a lagoon of impossible green.
The Andaman’s great reveal
Eighty metres of dark, then the sky opens.
Tham Morakot — the Emerald Cave — is the single most memorable half-hour in the Trang islands. You slip off the boat at the cliff face, swim into a sea tunnel that quickly goes black, follow your captain’s torch around a bend, and surface inside a hidden lagoon: a circle of white sand, green water and jungle-topped limestone walls open to the sky. Legend says pirates hid treasure here. Today the treasure is simply being inside it before anyone else arrives.
The day, from The Sunny Hill
The Emerald Cave is a tide table before it is a destination, so the concierge sets your departure to arrive at low water, early — usually leaving the pier not long after breakfast. Twenty minutes inside the lagoon is enough; then the boat rounds the island to Hat Farang, Koh Mook’s finest beach, a west-facing bay of soft sand and calm water flanked by cliffs, with a couple of easy-going beach restaurants for lunch if you prefer them to our picnic.
Koh Mook itself is a lived-in island — a Muslim fishing village on the east coast, rubber plantations, a few small resorts — and a walk or motorbike-taxi across it is a pleasant window into everyday Trang life.
Snorkelling on the way
Koh Waen and Koh Chueak sit almost on the route: tiny limestone islets wrapped in soft coral with dense schools of fish, and the classic stops for a swim before or after the cave. Add Koh Kradan, fifteen minutes further on, and you have the definitive Trang island day.
Good to know
- Life jackets are mandatory inside the tunnel and are provided.
- The cave lies within Hat Chao Mai National Park; the entry fee is settled by the concierge with the boat.
- On rough days or spring high tides the cave is closed to swimmers — we will tell you the night before and offer Kradan or Ngai instead.
Emerald Cave — quick answers
Do I need to be a strong swimmer for the Emerald Cave?
You need to be comfortable in the sea for around 80 metres, part of it in darkness, wearing a life jacket. Your captain guides the group through with a torch and a rope where needed. It is not for very young children or anyone anxious in the water — those guests can wait on the boat or on Farang Beach.
When is the best time to visit the Emerald Cave?
At low tide, early. The tunnel is only passable when the water is low enough to leave air above it, and by mid-morning day-trip boats from Koh Lanta arrive. We time your private longtail to be there first.
How long is the trip from The Sunny Hill?
Koh Mook is about 11 nautical miles from the coast below the hill — around 40 to 50 minutes by longtail.
Keep exploring
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