About Secret Reef
Secret Reef, nestled adjacent to Hin Raab South, is a captivating dive site close to Koh Chang, forming a unified, diverse underwater ecosystem. It is celebrated for its unique coral canyons, where whip corals gently sway and flower and spiny cabbage corals thrive, creating a macro paradise. This site boasts a shallow plateau at 5-6 meters and a maximum depth of 12 meters, making it ideal for Open Water divers, try dives, and those seeking a tranquil, uncrowded experience. The underwater topography includes distinct canyons that guide divers across the reef. Marine life encounters are frequent, with colorful nudibranchs adorning surfaces, blue-spotted stingrays resting on the sand, and moray eels peeking from their shelters. Barracudas are also spotted patrolling the reef edges, adding to the site's rich biodiversity. Divers can explore historical remnants, including an ancient teapot and scattered gunship bullets, providing a glimpse into the area's past. Combining Secret Reef with Hin Raab South allows for extended bottom time, making it perfect for thorough exploration and underwater photography.
Highlights
Season calendar
Nov – Apr (Peak)
Best visibility 25–30m, calm Andaman Sea. Similan & Surin Islands open. Whale sharks and manta rays at Richelieu Rock.
May (Transition)
Similan season opening/closing. Variable conditions, occasional rain. Still good diving at coastal sites.
Jun – Oct (Monsoon)
SW Monsoon brings rough seas. Similan Islands CLOSED. Gulf coast (Koh Tao) still diveable Jun–Sep.
Dive site facts: Secret Reef
- Depth
- 5–12 m
- Current
- Mild to none
- Entry
- Mooring line descent
- Level
- Open Water Diver, Try Dives
- Dive type
- Reef, macro, coral canyon
- Region / port
- Koh Chang, Eastern Gulf of Thailand
- Coordinates
- 8.6886° N, 98.0460° E
Conditions & Currents
Secret Reef is generally known for its suitability for relaxed exploration, suggesting minimal to no significant currents. It offers conditions that are favorable for Open Water divers, implying that strong, challenging currents are not a predominant feature of the site. Calm conditions are expected, allowing for comfortable navigation through the coral canyons and over the shallow plateau. The site's nature permits extended bottom time, further indicating stable underwater environments without demanding current scenarios that would limit dive duration. Divers should still remain aware of any localized water movements typical of reef structures and consult with local dive guides regarding daily conditions.
Marine life & sighting chances

Nudibranchs
common
Blue-spotted stingrays
common
Moray eels
occasional
Barracudas
occasional
Whip corals
common
Flower corals
common
Spiny cabbage corals
commonDive profile & how the dive runs
Begin your dive with a descent along the mooring line, targeting a depth of approximately 12 meters. From this point, navigate the distinct coral canyons that meander across the reef, providing a natural guided path. Along the route, explore the vibrant coral gardens and search for unique site features such as an ancient teapot and scattered gunship bullets. The dive includes exploring a shallow plateau found at 5-6 meters, which is ideal for extending bottom time and allows for a gradual ascent. Conclude the dive by returning to the mooring line, where the safety stop is performed, ensuring a smooth and controlled ascent.
Underwater photography
Secret Reef is particularly rewarding for macro photography, given the abundance of colorful nudibranchs that dot the reef. A macro lens will allow you to capture intricate details of these tiny creatures, as well as the moray eels peeking from crevices and the vibrant coral polyps. For wider shots of the coral canyons and blue-spotted stingrays on the sandy bottom, a wide-angle or standard lens can be effective. Consider using a strobe or video lights to bring out the true colors of the corals and marine life, especially in deeper sections or within the canyons. Practice excellent buoyancy control to avoid disturbing delicate corals and to get close enough to small subjects without stirring up sediment.
Combine with nearby dive sites
- Hin Raab South
Connected and often combined with Secret Reef for extended exploration.
- HTMS Sattakut Wreck
The HTMS Sattakut Wreck is a 48-meter long, decommissioned U.S.
- King Cruiser Wreck
The King Cruiser Wreck, a former 85-meter car and passenger ferry, transformed into one of Thailand's most celebrated artificial reefs…
- Shark Point
Shark Point is an exceptional dive site located within the highly protected Jardines de la Reina Marine Park off Cuba's southern coast.
- Koh Dok Mai
Koh Dok Mai, meaning 'Flower Island,' is a distinctive limestone outcrop located in Thailand's Andaman Sea, between Phuket and Phi Phi…
Getting there & logistics
Access to Secret Reef is typically arranged through dive centers operating from Koh Chang, a popular island in the Eastern Gulf of Thailand. Koh Chang itself is part of the Mu Koh Chang National Marine Park, which is a prime diving region in the area. Divers usually fly into Bangkok's Suvarnabhumi International Airport (BKK), which serves as the main gateway to the country. From Bangkok, domestic travel options to Koh Chang are available, though specifics like flight duration or ferry connections are not detailed for this specific site. Day trips are common, as Secret Reef can be explored in combination with its adjacent site, Hin Raab South, allowing for a comprehensive two-dive day. Permit and park fees for the national marine park are generally required.
Safety & environment
While Secret Reef is considered suitable for Open Water divers, general dive safety protocols apply. Divers should ensure they have adequate insurance covering dive accidents and potential evacuation, as recompression chambers in Thailand are primarily located in major hubs like Phuket and Pattaya, implying a potentially distant evacuation in emergencies from Koh Chang. Site-specific hazards are minimal, given the shallow depths and generally mild currents, but divers should still maintain awareness of their surroundings within coral canyons. Adherence to a maximum depth of 12 meters is crucial. Always dive with a certified guide and follow their specific briefing regarding current conditions and site navigation. Good buoyancy control is essential to protect the delicate coral formations and avoid disturbing marine life or kicking up sediment.
Who it suits, and who it doesn't
Suited for
- Open Water certified divers
- Divers seeking relaxed exploration
- Macro photography enthusiasts
- Beginners and try divers
- Those interested in marine history artifacts
Less suited for
- Advanced divers seeking extreme depths
- Divers primarily looking for strong currents and pelagic action
- Snorkelers (due to site description)
- Divers preferring extremely remote, untouched sites
FAQ
Secret Reef FAQ
What is the maximum depth at Secret Reef?
What marine life can I expect to see at Secret Reef?
Is Secret Reef suitable for beginner divers?
Are there any unique features at Secret Reef?
How is Secret Reef typically dived?
Why dive Secret Reef from a liveaboard?
Secret Reef is one of Thailand's signature dive sites. A liveaboard sleeps you on the water and puts you in the water for three to four guided dives per day, including dawn and night dives that day-boat operators rarely offer. You skip the daily commute back to port and reach quieter, less-crowded sites in the same region on a single trip.
Below are the liveaboards that include Secret Reef on their Thailand itineraries.
Liveaboards diving Secret Reef
These liveaboards may visit Secret Reef on selected itineraries, the exact dive sites depend on departure, weather and conditions.

Mandarin Queen 9
Thailand

Dolphin Queen
Thailand

Manta Queen 8
Thailand

The Junk
Thailand

Deep Andaman Queen
Thailand

Camic
Thailand

Lapat
Thailand

Explorer
Thailand

Andaman
Thailand

Stingray
Thailand

Seatopia
Thailand

Bunmee 4
Thailand
Dive sites similar to Secret Reef
Anemone Reef
Thailand
Anemone Reef, locally known as "Hin Jom" or "submerged rock," is a significant limestone pinnacle entirely hidden beneath the Andaman Sea's surface.
- Suitable for
- Intermediate
- Current
- Ripping
- Access
- Liveaboard or dayboat
- Depth
- 5–26 m
- Theme
- Pinnacle / Wall
Ang Thong, Wao Island
Thailand
Wao Island, nestled within the picturesque Ang Thong National Marine Park, is a captivating dive site characterized by its dramatic limestone formations and intricate underwater landscape.
- Suitable for
- Beginner
- Current
- Strong
- Access
- Liveaboard or dayboat
- Depth
- 3–20 m
- Theme
- Cave & cavern / Reef
Beacon Reef
Thailand
Beacon Reef, sometimes referred to as Beacon Bay or Beacon Point, is a cherished dive site within Thailand's Similan Islands National Park.
- Suitable for
- Beginner
- Current
- Moderate
- Access
- Liveaboard or dayboat
- Depth
- 5–25 m
- Theme
- Reef / Wreck
Breakfast Bend
Thailand
Breakfast Bend, also known as Three Trees, is a highly regarded dive site located along the eastern side of Similan Island No. 9, Koh Bangu.
- Suitable for
- Beginner
- Current
- Strong
- Access
- Liveaboard or dayboat
- Depth
- 5–25 m
- Theme
- Reef
Christmas Point
Thailand
Christmas Point, located on Similan Island number 9 (Koh Ba-Ngu), stands out as one of the Similan Islands' most iconic dive sites.
- Suitable for
- Intermediate
- Current
- Strong
- Access
- Liveaboard or dayboat
- Depth
- 2–40 m
- Theme
- Pinnacle
Chumphon Pinnacle
Thailand
Chumphon Pinnacle is a renowned deep dive site situated approximately 12 kilometers northwest of Koh Tao in the Gulf of Thailand.
- Suitable for
- Intermediate
- Current
- Strong
- Access
- Liveaboard or dayboat
- Depth
- 12–36 m
- Theme
- Pinnacle