The longest submerged cave system in Sweden, named Dolinsjögrottan, is located deep in the Bjurälven valley in the Jämtland mountains. The Bjurälven River, from which the valley takes its name, along with numerous streams, cut through the limestone rocks, carving underground passages.

Since the discovery of the cave's entrance in 1979, explorers have sought ways to explore it, but the very high water flow inside (over 20 knots) during summer made any attempts impossible. In winter, the flow is much lower, but the location's significant distance from civilization and the extreme cold significantly hinder exploration. All this meant that it was not until 2007 that the caves of the Dolinsjögrottan system began to be regularly explored.

The caves of the Bjurälven valley are explored by members of the Swedish Speleological Society (SSF) and others, selected depending on the goals of the expedition. One invaluable factor is the support of the residents of the Stora Blåsjön settlement, who help organize expeditions each year and share their knowledge.

During the very cold Swedish winters, the low flow means that access to the caves is still difficult, but feasible. However, expedition members face a series of other problems caused by heavy snowfall and very low temperatures of both air (even down to -20°C) and water (close to 0°C). Equipment is transported to the site using snowmobiles, which in deep snow requires both immense skill and good condition.

The longest discovered cave, Dolinsjö, is unlike the karst caves of Mexico or Florida, and its exploration requires combining dry speleology techniques with truly expert-level cave diving. Due to the number of tight restrictions, dives are performed in a sidemount configuration. Accessing the interior of the cave requires passing through a narrow entrance passage about 50 meters long. Although the cave is larger in further parts, there are also many tight restrictions there.

Thanks to the commitment of the Bjurälven team members and a series of expeditions from 2016-2022, the total length of the discovered cave passages has been extended to nearly 2.5 km. The expeditions also conducted reconnaissance in other caves in the valley to assess their exploratory potential. Additionally, two new entrances were identified.