Doubs and Jura · about 13 km from Vallorbe (CH)
Source du Doubs (Mouthe)
- Max depth92 m
- CertificationFull cave
- Water temperature≈ 5–6 °Cestimated, no reports yet
- SpecialExperienced divers
Diving and fills
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Fills nearby
- plongee.ch (Puidoux/Rivaz, Zwitserland)Air, nitrox, heliox, trimix, O₂ and helium; 200 and 300 bar outlets
- DiveStation (Neuchâtel, Zwitserland)Air, nitrox and trimix up to 300 bar; nitrox and trimix only during opening hours. O₂: ask.
The dive
At the spring you mostly see a shallow, bright blue pool at the foot of Mont Risoux; the sumps lie behind it. The water is 5–6 °C all year, and in November 2007 the diver's regulators froze in the -6 °C outside air.
1 earlier accident or incident has been reported at this cave. Read what happened ↓
Profile and sections
At the spring you mostly see a shallow, bright blue pool at the foot of Mont Risoux; the sumps lie behind it. The water is 5–6 °C all year, and in November 2007 the diver's regulators froze in the -6 °C outside air.
This is where the Doubs rises, at 945.5 m altitude and ~5 km from the Swiss border, from a cavity in Portlandian limestone. J.J. Bolanz reached the blockage at -55 m. In November 2007, after several trips called off by high water, John Volanthen got past it and laid 150 m of new line; he turned back to limit his decompression.
Practical: Volanthen followed the conditions through a regional webcam and a gauging station on the Doubs downstream.
- Depth and profile
- Plan for -92 m: in September 2009 a diver reached -92 m 1,395 m from the entrance, on a 7 h 30 dive in 6 °C water (FFS); an older guide gave -70 m. Per a 2007 dive report two sumps: S1 at the entrance, then in S2 a rift and a shaft to -40 m, with the way on at the floor at -45 m. Within 50 m of the shaft a squeeze between boulders; the old end point is a boulder blockage at -55 m, 250 m into S2, beyond which a ~3 x 3 m passage continues (150 m lined in 2007). Wikipedia describes a series of sumps, the third dropping vertically to more than -50 m. Per the 2007 report the cave does not go that deep.
- Configuration
- Per André Gloor the first squeeze can be passed with back-mounted cylinders; at the -55 m blockage the diver had to remove a cylinder in 2007. He dived a rebreather with trimix diluent and stage cylinders. Breakdown to the right at the foot of the shaft might go in sidemount but is unexplored.
- DPV: Not DPV-suitable (estimate)
- Squeezes between boulders and a blockage where a cylinder has to come off: no scooter. Volanthen did plan a return with a scooter for the far section in 2007.
- Gas
- Trimix from 40 m
Who can dive where
- At least Full cave
- Configurations: Backmount / twinset / Sidemount / CCR / Small cylinders / no-mount (speleo sumps)
- Configuration unknown — research beforehand
- Goes down to 92 m (trimix or deco may be needed)
- Experienced divers only
This is how the planner decides who in your team may dive this cave. Rules your own trip adds (organizer, a mail, the AI) show with your trip.
How to get there
The spring is on the Rue de la Source du Doubs in Mouthe, open and free for visitors. Diving needs the permission of the mayor (maire) of Mouthe. Give the mairie the dates and times of your dive and your diving certifications; apply by post (Mairie, 3 Grande Rue, 25240 Mouthe) or by e-mail (commune@mouthe.fr). Then confirm the dates and times with the gendarmerie of Mouthe. Park at the Grand Chalet car park and carry your equipment up on foot.
Around Source du Doubs (Mouthe)
Fills2 fill stations · nearest 49 km
plongee.ch (Puidoux/Rivaz, Zwitserland)
Route du Verney 18, 1070 Puidoux, Switzerland
Air, nitrox, heliox, trimix, O₂ and helium; 200 and 300 bar outlets
Mon–Fri 9:00–12:00 and 13:30–18:30, Sat 9:00–16:00; air station 24/7 for subscribers
Dive shop in Puidoux (Rivaz); one of the most complete gas lists in the area. Air-station subscription CHF 180 a year (couple CHF 290); air CHF 6–12 per cylinder, +CHF 2 for 300 bar. Walk-in trimix fills for visitors: ask.
DiveStation (Neuchâtel, Zwitserland)
Route de la Pierre-à-Mazel 4, 2000 Neuchâtel, Switzerland
Air, nitrox and trimix up to 300 bar; nitrox and trimix only during opening hours. O₂: ask.
Tue–Fri 9:00–12:00 and 13:30–18:30, Sat 9:00–16:00; air station 24/7 (subscription: ask)
Dive shop with a fill station; formerly the Neuchâtel branch of plongee.ch. The nearest known trimix address. CCR supplies (sorb) and walk-in fills for visitors: ask.
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News
All (1)
Accidents and incidents
What happened at this cave before, with the sources. No names are given; read it as a lesson for your own planning.
- Fatal accident, September 2008: an English diver (32) from a group of five foreign divers did not surface with the others; his companions found him at 30 m and he could not be saved.
Access and rules change: check what applies locally right before your trip. Source: GDELT Project and the news feeds of diving magazines. Search for more news ↗ Searched automatically, last on 5 Nov 2026.
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