Pluragrotta

Per NGDF, Pluragrotta is the largest and best-known diveable cave in Norway: marble passages where the Plura river emerges. Arctic char swim at the entrance. Plura Valley has its own names for the parts of the cave. After about 300 m the Spiral begins, a jump that starts at 6 m and meets the main line at -24 m; the first section has ten jumps over 470 m. Further into the mountain lie the Pressure tube, 800 m in at 15 m deep, and the Mud Run, one of the very few places in Plura where you can lose all visibility to silt. Visibility is usually 30–50 m (Plura Valley gives an average of 35 m) and in winter up to ~100 m (peak season; March–April according to Plura Valley); during the May snowmelt it can drop to 2–3 m, and it is also less after heavy rain. The flow has been low since Kallvatnet was dammed in 1966: from ~20,000 down to ~1,000 m³ a minute.

The first known dive was in 1980 (Svein Grundstrøm and Bjørn Fagertun). From 1987 ten Norwegian divers, mostly from the Oslo fire brigade, explored the system at their own expense; by 1997 they had surveyed almost 3 km. Finnish explorers found the connection with Steinugleflåget in September 2013; from the dry side that pool takes a vertical climb of over 100 m. The family of the Jordbru farm opened the dive centre in December 2016, the world's first Arctic cave diving centre. In August 2019 an underwater wedding with 69 participants was held in the air chamber, 450 m into the cave (a Guinness world record); the air chamber is named the Chapel after it. On 29 March 2024 saxophonist Hakon Erlandsen and bassist Davide Bertolini played a concert there, streamed live, for an audience of certified cave divers. The 2014 accident and the recovery that followed are the subject of the documentary Diving into the Unknown (Juan Reina, 2016).

Practical: today you dive Pluragrotta through Plura Valley. Without a cave certification you can dive the pool in front of the entrance, or the cavern zone with an experienced cave diver; ice diving in winter. Plura Valley offers packages of 3, 5 or 7 dive days with a guide, food, air, oxygen and nitrox (no helium), rental cylinders, beds and transfers from and to the airport (Mo i Rana or Hemavan); the longest also has two dives in Litjåga. There are 20 beds, a lounge and a sauna by the river, and Plura Valley fills gas. NGDF's annual 'Plurauka' (August, 50–70 divers) is no longer held.