Thale Nai Mae Koh Island or Emerald Lagoon is a large saltwater pool in the middle of Mae Koh Island, 200 meters wide, 250 meters long, and 7 meters deep. The dark green water reflects the surrounding limestone cliffs.

Secret Underwater Tunnel: Underneath the water, there is a rock cavity connecting to the outer sea. The water circulates regularly, allowing small marine animals such as hermit crabs and small fish to live there. Most tourists are unaware of this vibrant ecosystem.

Path to the Viewpoint: Tourists climb steep wooden stairs to the highest viewpoint, revealing views on two sides. One side is the vast Gulf of Thailand, and the other is the tranquil inland sea, like a forgotten world.

Fragility of the Ecosystem: Water flowing in and out of the rock cavity creates a life cycle for small marine animals. Although swimming is not allowed, admiring the emerald surface of the water from the viewpoint is enough to impress tourists.

Perspective Tourists Often Miss: Observe the reflection of the water surface in the morning to see different shades of emerald green. And in the afternoon, the sunlight shines on the cliffs, revealing ancient patterns on the rock walls.

Extra Tip: Bring a polarizing filter camera to capture the emerald color and patterns under the water's surface clearly. Some tourists don't know that from this angle, you can see small fish swimming near the surface.

• From Koh Samui or Koh Phangan, buy a One Day Trip tour (speedboat or tour boat) departing from Nathon Pier. It takes approximately 1 hour.

• Wear sturdy shoes as some sections of the wooden stairs are steep.

• Bring drinking water as the hot weather may cause excessive sweating.

• February–September is when the emerald water is clearest and most beautiful.

• Avoid sunscreen with chemicals that are harmful to coral before swimming in the sea around the island.

Park Entrance Fee:

• Thai citizens: Adults 40 baht / Children 20 baht

• Foreigners: Adults 300 baht / Children 150 baht

Opening Hours:

• Open daily: 08:00 – 17:00 (Last admission according to tour boat schedules)
  Note: Closed during the monsoon season, November – December of each year