Koh Mae Ko: The Emerald Lagoon

Famous for Talay Nai — a spectacular landlocked saltwater lake — and its vibrant coral reefs. The visual heart of Ang Thong Marine Park.

The Highlights of Koh Mae Ko

Koh Mae Ko (Mother Island) is perhaps the most photographed island in the entire national park. Its unique geography features a hidden, landlocked emerald lake surrounded by sheer limestone cliffs, connected to the sea through underground tunnels.

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Whether you're arriving by big boat or speedboat, the short but steep climb to the lagoon viewpoint is a non-negotiable part of the experience. The island also offers some of the park's best shallow-water snorkelling right off its landing beach.

  • Talay Nai (Emerald Lagoon): A stunning landlocked lake with water of an impossible green hue.
  • Lagoon Viewpoint: A 10-15 minute climb on wooden steps for the classic "island within an island" shot.
  • Beach Snorkelling: Diverse reef fish and soft corals just meters from the sand.
  • Kayaking Base: Many tours use the sheltered waters here as a starting point for coastal paddling.

    • Visiting the Emerald Lagoon (Talay Nai)

    A short but intense climb rewarded by one of Thailand's most unique natural wonders.

    The Hike Experience

    The path to the lagoon is entirely on well-maintained wooden and concrete steps. It is steep, but much shorter than the 500m viewpoint at Koh Wua Ta Lap.

    1

    The First Ascent

    About 5-7 minutes of steep climbing. This leads to the main viewpoint overlooking the lagoon.

    2

    The Viewpoint

    From here, you can see the lagoon on one side and the open sea on the other. Breathtaking.

    3

    Descent to the Water

    You can continue down the other side of the ridge right to the edge of the lagoon itself. Note: Swimming in the lagoon is strictly prohibited to preserve the ecosystem.

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    Practical Tips

    Visibility: The color of the lagoon changes with the sunlight. Mid-morning is best for the brightest emerald tones.
    Shoes: While wooden steps are easier than rock, they can be slippery when wet. Wear shoes with decent grip.
    Photography: A wide-angle lens is essential to capture the full scale of the lagoon and its cliffs.

    Lagoon Viewpoint — Koh Mae Ko

    Worth Adding to Your Itinerary

    The Emerald Lake is one stop on a bigger day.

    The Emerald Lake (Talay Nai) on Koh Mae Ko is a highlight of every Ang Thong Marine Park tour, alongside the Pha Jun Jaras viewpoint on Koh Wua Talap, snorkelling at Koh Wao and sea kayaking. Day trips run from Koh Samui and Koh Phangan — see live options below.

    Common Question

    No — swimming in Talay Nai (the Emerald Lagoon) is strictly prohibited to protect the fragile, landlocked ecosystem. You view it from the ridge after the short climb, and on some tours can walk down to the water's edge, but entering it is not permitted on any tour. The nearby beach at the landing point is where you snorkel and swim instead — see our snorkelling guide for what to expect underwater.
    About 5–7 minutes of steep climbing on well-maintained wooden and concrete steps gets you to the main viewpoint — considerably shorter than the 500m viewpoint hike at Koh Wua Ta Lap. Wear proper shoes with grip, since the steps can be slippery when wet, and go mid-morning for the brightest emerald colour in the water.

    Experience Koh Mae Ko

    The Emerald Lagoon is included in almost every full-day tour. Compare the best options below.

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