About This Route
Lake Thun, or Thunersee, sits at 558 meters elevation in the Bernese Oberland region of the Swiss Alps, offering crystal-clear waters and iconic dive sites like the wreck of the paddle steamer Greif, sunk in 1919 near Interlaken. This Bernese lake spans 48 square kilometers with depths up to 217 meters, attracting divers for its visibility often exceeding 20 meters and alpine backdrop of Eiger, Mönch, and Jungfrau peaks. Popular entry points include Gwatt and Bödeli, accessible by car or train from Interlaken Ost station. As a moderate-altitude site, Lake Thun demands PADI Altitude Diver awareness; follow protocols from Divers Alert Network (DAN Europe) for adjusted no-decompression limits. Expect water temperatures from 4°C in spring to 20°C in late summer, with thermoclines creating sharp layers.
Safety Considerations
High-altitude diving alters nitrogen absorption rates; use a dive computer set to altitude mode or PADI altitude tables for profiles above 300 meters. Visibility drops near river inflows like the Aare, where silt reduces sightlines to under 5 meters. Boat traffic peaks in summer; dive with a surface marker buoy (SMB) and flag to signal your position. Hypothermia risks rise below 12°C; limit bottom times to 30-45 minutes. Follow Leave No Trace by avoiding disturbance to perch, pike, and coregonus fish populations. Check Swiss Federal Office of Meteorology forecasts for sudden katabatic winds from surrounding peaks. Certification minimum: Advanced Open Water with drysuit or altitude specialty recommended. Buddy diving is mandatory; brief on ascent rates not exceeding 9 meters per minute.
Essential Gear
Pack a drysuit from brands like Waterproof or Bare for thermal protection, paired with 5mm neoprene hood, gloves, and boots. A dive computer like Shearwater Peregrine with altitude algorithm is critical. Include redundant air sources (pony bottle), lift bag for wrecks, and dive light for exploring the Greif's interior. Reel and guideline prevent silting in low-vis zones.
Emergency Tips
In decompression sickness (DCS) symptoms like joint pain or numbness, ascend slowly, administer 100% oxygen if available, and call 144 for Swiss ambulance; nearest hyperbaric chamber is in Bern University Hospital, 45 minutes drive. Signal emergencies with three blasts on rattle or up/down SMB pulls. DAN Europe hotline: +39 0471 977788.
This guide ensures safe exploration of Lake Thun's underwater heritage while prioritizing risk mitigation, drawing from PADI standards and local dive center reports from Thun Divers.