Exploring caves is never something to be taken lightly—especially when it requires diving beneath the surface. Cave diving demands special skills, precise techniques, and a high tolerance for risk. This is the story of an expedition into Sweden’s water-filled caves, believed to form the country’s largest underwater cave system.
They call it the Bjurälven Expedition, named after the Bjurälven Valley where the exploration takes place. The region has long been known for its cave networks. Records of explorations here date back to the mid-20th century, and researchers believe that all the caves in the valley may be connected, forming one massive system.
The last major breakthrough came in 2007, when a group of cavers began investigating submerged passages in the Jämtland Mountains of central Sweden. To their surprise, the expedition revealed the country’s largest underwater cave system. Fifteen years later, they are still exploring it—and most recently, they returned in March and April 2024.
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Two New Caves
Their 13th expedition began on March 25, 2024. A team of 20 set out to explore Bjurälvsgrotten and Festins caves.
The first challenge was familiar: both entrances were buried under deep snow, and access to the remote site was far from easy. The team rode snowmobiles into the northwestern Jämtland mountains, then spent hours shoveling through several meters of snow and summer debris blocking the entrances. Only then could they begin their reconnaissance dives, setting up equipment and placing spare air tanks in mapped areas.
The passages inside were extremely narrow. To advance, divers had to squeeze through sumps—flooded tunnels—sometimes crawling or dragging equipment while wearing full scuba gear. Water temperatures hovered around 0°C, forcing everyone into drysuits for survival.
A Virgin Cave
On the third day, the team managed to push deeper into both caves. Bjurälvsgrotten proved to be the tougher challenge, requiring each diver to descend a 10-meter vertical drop into a waterfall before laying down guide ropes. They also had to dig through obstructions to widen access for the rest of the team.
Throughout the week-long mission, strong currents made diving in Bjurälvsgrotten especially difficult, while Festins offered smoother progress. After five days, the team managed to complete a 30-meter survey of unexplored passage.
“Thirty meters doesn’t sound like much,” one diver explained, “but it takes enormous effort to map every single meter of untouched cave.”
At the end of the expedition, both teams conducted preliminary dives in Meandergrottan, the outlet of the Bjurälven River. They hope to return and expand their survey of that system in the future.
So far, the theory of a vast, interconnected system still holds. To date, explorers have mapped 2.43 kilometers of linked passages—making it Sweden’s longest underwater cave. How far it extends remains a mystery. The team plans to keep searching in the years ahead. (Sulung Prasetyo)
