Dive Site: Koh Tao — Green Rock

About Koh Tao — Green Rock

Green Rock, situated off the west coast of Koh Tao near Koh Nang Yuan, is a unique dive site characterized by a striking cluster of granite boulders. This site offers an adventure-filled experience with its natural network of swim-throughs, caverns, and narrow passages, making it a highly interactive underwater landscape. Depths vary from 4 meters down to approximately 30 meters, accommodating both newer and experienced divers. The topography is its defining feature: a chaotic pile of granite formations that create a maze-like environment. Divers can explore numerous tunnels and hidden chambers, revealing different aspects of the reef community with each visit. The site is known for its resident triggerfish, especially titan and yellow margin triggerfish, which are more territorial during nesting season. Beyond these, you can find blue-spotted stingrays, moray eels, groupers, and schools of barracuda and fusiliers. Conditions are generally calm and the site is diveable in various weather, though strong winds from June to August, and mid-November to early January can make it inaccessible. Visibility typically ranges from 10 to 25 meters, and water temperatures are a comfortable 27–30°C year-round. While Open Water divers can enjoy the shallower parts, an Advanced Open Water certification is recommended for deeper explorations and more complex swim-throughs. Green Rock is an ideal spot for those seeking discovery and interaction with the underwater environment. Its intricate structure rewards careful navigation and offers a dynamic dive where no two trips are ever quite the same. It's often combined with a dive to Chumphon Pinnacle for a full morning trip.

Dive site facts: Koh Tao — Green Rock

Depth

4–30 m

Typical dive

12–25 m, 50–60 min

Current

Mild to variable

Visibility

10–25 m

Water temperature

27–30°C

Entry

Boat

Level

Open Water with experience / AOWD recommended

Dive type

Boulder formations, swim-throughs, reef

Region / port

Koh Tao, Thailand

Coordinates

10.1256, 99.8156

Conditions & Currents

Currents at Green Rock are typically mild but can vary, occasionally sweeping through the channels and bringing increased fish activity. The site is generally sheltered, offering good visibility between 10–25 meters, although strong winds and waves, especially between June to August and mid-November to early January, can make the site inaccessible. Water temperatures remain consistently warm, ranging from 27–30°C throughout the year. Divers should be aware of triggerfish nesting areas, particularly between 16 and 25 meters, where these fish can be territorial. Good buoyancy control is essential for navigating the numerous swim-throughs and managing encounters with potentially defensive marine life.

Marine life & sighting chances

Titan triggerfish

Nesting season (June-September) · common

Yellow margin triggerfish

Nesting season · common

Blue-spotted stingray

occasional

Moray eel

common

Giant grouper

occasional

Yellowtail barracuda

common

Fusilier

common

Trevally

common

Nudibranch

occasional

Shrimp

occasional

Scorpionfish

occasional

Pipefish

occasional

Hawksbill turtle

common

Green turtle

common

Dive profile & how the dive runs

Dives at Green Rock typically begin on the north side, descending through a canyon formed by massive granite boulders. From there, divers navigate through an intricate network of swim-throughs, tunnels, and caverns that define the site. The route progresses through various gaps, some wide and others requiring careful fin control, eventually reaching deeper sections down to 25-30 meters. The deeper areas feature the 'Trigger Pit,' a sandy expanse with triggerfish nests between 16-25 meters. Divers explore the rock formations, observing marine life tucked into crevices and hidden chambers. The turn point often depends on air consumption and the group's comfort with deeper exploration. Ascent usually involves making your way back towards shallower parts of the rock, allowing for an extended safety stop in the 5-meter zone where the rock tops offer additional marine life viewing before surfacing.

Underwater photography

Green Rock offers exceptional opportunities for both wide-angle and macro photography due to its diverse topography and marine life. For wide-angle shots, a fisheye lens is ideal to capture the grandeur of the granite swim-throughs and the dramatic interplay of light and shadow within the caverns. You'll want to ensure good buoyancy to navigate these tight spaces without disturbing the environment. For macro subjects, such as nudibranchs, shrimp, and pipefish hidden in crevices, a dedicated macro lens will be essential. Bringing a powerful torch is highly recommended to illuminate darker areas within the swim-throughs and bring out the true colors of resident marine life. Patience is key when photographing triggerfish, especially during nesting season; maintain a respectful distance to avoid aggressive encounters. Pay attention to schools of barracuda and fusiliers in the open water for dynamic compositions.

Combine with nearby dive sites

• Chumphon Pinnacle

  Often combined with Green Rock as a two-dive trip

• Koh Tao — Japanese Garden

  Ideal for beginners, known for coral formations

• Koh Tao — Twins

  Versatile site near Koh Nang Yuan, suitable for all levels

• Sail Rock

  Further afield, known for schools of fish and a chimney swim-through

• Elephant Head Rock

  Another Koh Tao site with rock formations

Getting there & logistics

Green Rock is located just a short 15–30 minute boat ride from Koh Tao, making it easily accessible for half-day dive trips. Most dive operators on Koh Tao, departing from Mae Haad pier, offer morning two-dive excursions that typically return by midday. A common itinerary pairs Green Rock with Chumphon Pinnacle. To reach Koh Tao, travelers typically fly into Koh Samui (USM) and then take a ferry, or travel by bus/train to Chumphon or Surat Thani, followed by a ferry. No specific permits are mentioned for Green Rock, but standard Thai diving regulations apply. Trips are often bundled with equipment rental and guides. Travelers should budget for these costs, as well as accommodation on Koh Tao.

Safety & environment

While Green Rock is generally safe, several factors require attention. The nearest recompression chamber is in Koh Samui, necessitating proper evacuation protocols for any diving emergencies. Dive insurance, such as DAN, is strongly recommended for all divers. Site-specific hazards include the potential for aggressive titan triggerfish, particularly during their nesting season from June to September. Divers must be briefed on how to react to triggerfish, which includes swimming laterally rather than vertically if charged. Navigating the swim-throughs requires good buoyancy control to prevent injury or damage to the environment. Always follow your dive guide's instructions and never enter areas beyond your training or comfort level.

Who it suits — and who it doesn't

FAQ

Koh Tao — Green Rock FAQ

Liveaboards diving Koh Tao — Green Rock

These liveaboards may visit Koh Tao — Green Rock on selected itineraries — the exact dive sites depend on departure, weather and conditions.

Mandarin Queen 9

Thailand

26 guests37.5 m

Manta Queen 8

Thailand

24 guests

$127/day

The Junk

Thailand

18 guests33 m

$163/day

Deep Andaman Queen

Thailand

23 guests30.5 m

$194/day

Explorer

Thailand

16 guests25 m

$150/day

Andaman

Thailand

20 guests26 m

$108/day

Stingray

Thailand

8 guests24 m

$245/day

Seatopia

Thailand

24 guests24 m