The period between 2016 and 2020 marks 30 years of British caving expeditions to Vietnam, moving beyond the established master systems into the rugged, less-accessible karst of Quang Ninh and Minh Hoa Districts.
While 2016 & 2018 were remarkable by the number of new caves found, 2019 & 2020 were special expeditions to remember for the caving team. A major highlight occurred in 2019 when the specialist diving team—famous for the Thai cave rescue—conducted deep-water dives in Son Doong and the Nuoc Mooc spring, both reaching depths exceeding 70 meters. Although the 2020 expedition was shortened by the global pandemic, the team still surveyed over 10km of new passages.
In 2016, a team of fifteen cavers returned to the jungle to investigate over 50 different cave entrances spread across various regions. This year was all about connecting the dots and finding new layers within the karst landscape. The team successfully explored several beautifully decorated dry caves and deep vertical shafts, including a significant new discovery reached by crossing a hidden valley beyond Hang Tien.
Rather than just finding small holes, the team pushed deep into existing systems, uncovering massive new corridors and active underground rivers. By the end of the expedition, they had surveyed a total of approximately 7 kilometers of new cave passages. These discoveries, ranging from remote stream sinks to high-level chambers above Hang En, proved that even well-known areas still held major secrets waiting to be mapped.
Hang Tien 2 Cave
Key Achievements
- Ruc Ma Rinh: Located at the edge of the limestone in the North West, this cave was explored for 1,316m. It is a technical river cave with cascades and a significant draught, left with a "big question mark" for future return.
- Hang Hoa Huong: This 2,876m system revealed large, well-decorated dry passages and a unique geological feature called the "Mud Cuillins" - a knife-edge arête of mud that required precarious traversing.
- Hang Tien 2: A significant extension bringing the cave to a length of 2,519m. The cave is a complex system of dry and active passages with exceptional formations. Technical challenges included a series of gour dams rising in steps of 3m and 8m; exploration was pushed forward by using a small sapling to scale these vertical calcite barriers.
- Dong Cay Sanh: Located near Road 20, Dong Cay Sanh is a 850m-long, well-decorated dry cave. The interior features a "crunchy calcite slope" leading to a thinner section of passage adorned with "magnificent eight metre high multi-coloured curtains".
Dong Cay Sanh
Over 30 entrances were explored and nearly 12 kilometres of new cave surveyed, in many parts of PNKB National Park. Ruc Ma Rinh Cave at Hoa Son was extended by 3350m to make it 4750m long and 170m deep. Hang Soong 639m, Hang Ken Dry 639m and Hang Rua extension 600m were surveyed in the Tu Lan area. A higher level in Phong Nha Cave was explored for 1km. Entrances to the West of the Chay River were explored. Ho Van Luc was 530m long. Hang Lang Phu Nhieu was explored for 697m, a small stream cave.
Key Achievements
- Hang Loi: Located approximately 100m from the entrance of Son Doong, this cave was explored for 1,928m. Despite reaching passages up to 110m wide and 80m tall, no physical connection to the Son Doong system was identified.
- Hang Phu Nhieu 1: A 697m stream cave explored near Phu Nhieu Village, leading through multiple split-levels and some different passages.
In this year a British diving team comprised of the cave divers that had rescued the Thai children trapped in a cave in Thailand dived both Son Doong Cave and the giant spring Nuoc Mooc. Both dives were very deep, over 70m deep.
Key Achievements
- Hang Son Doong Diving Expedition 2019
In 2019, Oxalis Adventure sponsored world-class cave divers Rick Stanton, Chris Jewell, and Jason Mallinson, who had joined the Tham Luang rescue in Thailand to survey Hang Son Doong’s terminal sump. The goal was to explore the underwater passage and its potential connections.
Despite visibility limited to just two meters, the team performed several technical dives. Martin Holroyd conducted the initial reconnaissance, followed by Chris Jewell at -60m. On April 3, Jason Mallinson reached -77 meters, setting a record for the deepest cave dive in Vietnam.
The team successfully extended the cave’s known passage by 60 meters, discovering a vast tunnel that turns sharply and continues to descend. While the roof was identified at -61 meters, the floor depth remains unknown. These findings confirm the cave system is even larger than previously recorded, with further exploration required in the future to map its full extent.
- Hang Soong: A 639m dry cave famous for numerous shallow gour pools filled with "coral towers". The interior features a floor of thousands of small orange cave pearls and is almost entirely covered in various forms of calcite.
- Ken Dry: Located behind Ken Cave after a trek up the hill, this 778m fossil passage is adorned with black and white popcorn coral and rare crystal bands.
- Hang Ho Van Luc: A 530m cave with nice dimensions and stunning decorations. It features a zigzagging morphology and a flowstone-rimmed pit leading to a collapsed lower level.
A Team of eleven cavers and one geologist returned to Quang Binh for this expedition. The first team set off for Quang Ninh District. More than a day’s walk led to a camp next to the river, with a large entrance in sight. This turned out to be a through cave previously explored, so the team set off again over the top of this cave and into the valley on the other side.
We noted a small stream entering on the right, which led to a new cave, Hang Nuoc Ngam. This cave was explored for 3872m to a boulder blockage. Further down the valley a large collapse dropped into the middle of another section of river cave. Nuoc Lan 3 was surveyed for 1919m to an exit. This small system, Rao May comprises four caves and a total length of 6255m.
The small village of Phu Nhieu also has a small system. Phu Nhieu 1 explored in 2018, and Phu Nhieu 2, 3 and 4 explored in 2020. Phu Nhieu 2 is 195m long with a small stream. Phu Nhieu 3 and 4 connect and the cave is 2012m long. Near Dai Cao, Hang Doc Co a well decorated drive cave was explored for 555m.
Although the 2020 expedition was cut a bit short by the start of the pandemic, 12 caves were explored and 10.5km surveyed.
Rao May
Key Achievements
- Hang Nuoc Ngam: A significant 3,872m river cave in the Quang Ninh District. It is characterized by its "cherty" obstacles and a massive breakdown chamber before ending in a sump.
- Nuoc Lan 3 (Rao May 3): A 1,919m river cave that forms part of the Rao May system (totaling 6,255m). Exploration required continuous swimming through corridors filled with enormous "rounded pale limestone boulders" and navigating fast-flowing cascades using floating ropes.
- Hang Phu Nhieu 3 & 4: A 2,012m system formed by the connection of Phu Nhieu 3 and Phu Nhieu 4. It features large walking streamways and diverse aquatic life, including fish, frogs, crabs and crayfish.
- Hang Doc Co (Grass Slope Cave): A beautifully decorated 555m dry cave found near Dai Cao, featuring columns, crystals, and rare trees at its entrance.
Hang Phu Nhieu 4
