Tonlé Sap (Mekong Basin) – Inland & Freshwater Diving Dive Site
Site Overview
Tonlé Sap (Mekong Basin) is a limited exploratory diving in the Mekong Basin with huge catfish and freshwater stingrays, mainly scientific expeditions with no established recreational infrastructure dive site in the Inland & Freshwater Diving region of Cambodia, situated among the diverse reef systems and island formations that make this Southeast Asian nation one of the Gulf of Thailand's most emerging diving destinations. The site features depths from 3 to 12 meters with an average depth of 7 meters, offering an extraordinary underwater experience showcasing the remarkable combination of fringing reefs, offshore islands, and historical wrecks that Cambodia's waters are celebrated for among adventurous divers seeking less-crowded tropical diving. Renowned for its encounters with Giant Mekong Catfish, Freshwater Stingray, Sawfish and other remarkable marine species, Tonlé Sap (Mekong Basin) attracts divers seeking thrilling underwater adventures in one of Southeast Asia's most distinctive and developing diving destinations. The Cambodian coast creates a fascinating underwater landscape of fringing reefs, rocky islands, artificial reef structures, and natural coral communities that provide habitat for diverse marine life in the warm waters of the Gulf of Thailand. The unique geography of Cambodia's coastline with its chain of offshore islands creates varied habitats supporting abundant marine life including tropical reef fish, sharks, rays, and pelagic visitors found in few other destinations. Visibility typically ranges between 5 and 30 metres depending on site location and season with the outer island sites offering the clearest water. Water temperatures range from 26 to 31 degrees Celsius year-round making a 3mm shorty standard equipment. Tonlé Sap (Mekong Basin) consistently ranks among the top dive sites in the Inland & Freshwater Diving region, drawing dedicated divers who seek exceptional reef diving experiences combining rich marine biodiversity with the excitement of exploring Cambodia's developing underwater frontier.
Dive Briefing
"A typical dive at Tonlé Sap (Mekong Basin) begins with entry from the dive boat, descending to the main formation at approximately 7 meters while orienting yourself and equalizing before exploring the remarkable Cambodian underwater landscape. Once established on the main formation, divers should swim along the reef structure or wreck exploring diverse habitats, moving between coral encrustations, swim-through sections, and sandy areas while maintaining excellent buoyancy control to protect the marine life colonising the structure below. The most productive depth zone is between 5 and 7 meters where the highest concentration of reef fish species and photographic opportunities are abundant. Navigate along the reef or wreck edge watching for pelagic species in the surrounding water, and check the overhangs, crevices, and ledges where moray eels, groupers, and larger reef fish shelter from the current. Cambodia's reef and wreck environments require careful awareness of marine life hazards and potential entanglement when exploring interior sections. Monitor depth and NDL particularly near 12 meters on the deeper sites, and always maintain a conservative approach to dive planning given the distance to the nearest hyperbaric facilities. Scan the surrounding water for approaching pelagic species including eagle rays and barracuda that patrol the reef edges. Conclude the dive with a slow ascent and a generous safety stop at 5 meters, deploying your DSMB before surfacing and signaling the dive boat for pickup."
Signature Marine Life
Giant Mekong Catfish
Pangasianodon gigas
Best: November, December, January
Freshwater Stingray
Himantura sp.
Best: November, December, January
Sawfish
Pristis sp.
Best: November, December, January
Butterflyfish
Chaetodon sp.
Best: November, December, January
Baitfish
Spratelloides sp.
Best: November, December, January
Anthias
Pseudanthias sp.
Best: November, December, January
Stingray
Taeniura lymma
Best: November, December, January
Nudibranch
Chromodoris sp.
Best: November, December, January
Safety & Hazards
- Freshwater diving environment requiring altitude dive computer settings and adjusted decompression planning
- Highly variable visibility from 1 to 10 metres in quarry water requiring close buddy contact and torch
- Submerged vehicles and structures with entanglement hazards requiring careful buoyancy and awareness
- Limited dive infrastructure and emergency medical facilities requiring self-sufficient equipment
- Hot tropical climate requiring hydration management between dives
Traveler Notes
Who is this for?
Tonlé Sap (Mekong Basin) is best suited for Advanced Open Water certified divers comfortable with moderate depths and current conditions at this Cambodian site. The site rewards experienced divers with dramatic reef structures, diverse marine communities, and the possibility of encounters with larger species including groupers, rays, and pelagic fish patrolling the surrounding water. Underwater photographers will find exceptional wide-angle opportunities with dramatic reef landscapes and wreck silhouettes as backdrops, while macro enthusiasts can document the extraordinary diversity of critters colonising the structures. Divers should be comfortable with drift diving techniques and DSMB deployment as conditions may require careful navigation.
Quick Stats
Dive Logistics
- Scuba Nation Siem Reap
- Angkor Dive Centre
Photography Info
Best for: unique, freshwater, wide_angle
Nearby Stay
Raffles Grand Hotel d'Angkor
Siem Reap • 5km away
Park Hyatt Siem Reap
Siem Reap • 3km away