Bjurälven is a long limestone area in Jämtland, northern Sweden, where a river sinks and flows underground, emerging 3km lower down in the valley. The existence of large water-filled cave passages is certain.

However, until recently nobody had managed to penetrate into the tunnels because of high water flow and the remoteness of the region, which is also a beautiful nature reserve. In early 2007 we performed our first winter expedition and our hope that the water flow would be lower was rewarded. The year after a larger expedition concluded that the area is unique to Sweden and which certainly contains Sweden’s longest underwater cave.

www.expeditionbjuralven.se

The 15 participants coming from all over Sweden and 8 are experienced cave divers. They are encountering extremes conditions. Some passages are so small that the divers have to take off their cylinders underwater and push them ahead as they inch slowly forwards.

The currents are still very strong even in winter and in places the divers must drag themselves forward using ropes. The water temperature is only just above freezing and as a wet diver climbs out of the water all equipment freezes instantly in temperatures which can dip below -15C.

Snow at least a meter deep and frequent snowstorms add to the difficulties.