Finland · about 2 km from Lohja
Ojamon kalkkikivikaivos (Ojamo)
- Max depth160 m
- CertificationIntro to cave
- Water temperature≈ 4–20 °C, varies with the seasonestimated, no reports yet
- SpecialDPV-suitable
Diving and fills
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Fills nearby
- Fill stationVaruste.net (Helsinki-Konala)Air (single and twin cylinders, max 20 l, no composite cylinders) and nitrox (single cylinder); trimix only as part of their tec courses, not as a walk-in fillRoute ↗
- Fill stationArctic Divers Dive Center (Helsinki)Air to 200 bar (€10–15) and to 300 bar (€10–20); nitrox, O₂ and trimix are not listed — askRoute ↗
What it looks like
Scuba diving in Ojamo Open Water, Lohja, Finland 22.12.2018 We are back in Ojamo mine diving 2024. This was filmed and edited with GoPro 10 & Quick app Ojamo-Negahelmet Ojamon kaivos, Lohja
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Videos and posts
From other divers, via YouTube, Instagram and Facebook. They only load when you click; after that, Google's or Meta's privacy rules apply.
Scuba diving in Ojamo Open Water, Lohja, Finland 22.12.2018 We are back in Ojamo mine diving 2024. This was filmed and edited with GoPro 10 & Quick app Ojamo-Negahelmet Ojamon kaivos, Lohja
Search for more onYouTube ↗Instagram ↗Facebook ↗
Other people's footage, not advice: how someone else dives here says nothing about what suits your team. Dive within your training.
The dive
The water in the mine is clear, ~4 °C at depth. The pit reaches ~20 °C in summer, but visibility then drops to ≤1 m (algae) and in autumn sometimes to near zero (humus).
1 earlier accident or incident has been reported at this cave. Read what happened ↓
Profile and sections
The water in the mine is clear, ~4 °C at depth. The pit reaches ~20 °C in summer, but visibility then drops to ≤1 m (algae) and in autumn sometimes to near zero (humus). Winter is clearest; you then dive under ice, with a hole kept open by pumps. You see rails and mine carts, tools, hanging lamps, dynamite boxes, the concrete wall 'Helvetin portti' at -45 m that holds back the lake, the rail and staircase shafts (Kiskokuilu, Pystykuilu) and the 13 halls of 'Helmet'. Sources describe the rock as stable, without supports. Less-visited drifts hold silt that your bubbles bring down from the ceiling.
Ojamo is a former limestone mine of Lohjan Kalkkitehdas: open pit from 1925, underground from 1931–33, closed in 1965 (8.7 Mt of limestone). In WWII it held a POW labour camp. It flooded when pumping stopped; the pit is now called Kaivoslampi. It has been dived for ~40 years, ~2,000 dives a year (city of Lohja, 2026). Per Yle (2017), the Montola mine near Pieksämäki is a comparable site.
Practical: the rules on ojamodive.fi (possibly from the previous operator) ask for a team with a dive leader and a safety diver ready within 1 minute, thirds on OC, and CCR divers keep enough bottom gas to surface. Dives >60 m or >180 min need a support team and backup deco gas at the surface; under ice with a surface line. Per Yle (2026), cave or mine training is required under ice.
- Depth and profile
- Open pit ~-6 m along the edges. Mine levels -28 m (Helmet: 13 halls in a row), -56/-58 m, -88 m (longest continuous stretch 1.7 km) and -138 m; shaft to ~-238 m (one source: ~-250 m). Most dives at -28, -38 and -58 m. Deepest recorded dive -160 m (2013).
- Configuration
- All configurations: roomy halls and drifts, with some narrow connections (e.g. 'Madon häntä', ~100 m). For the deep levels and long dives in ~4 °C water: CCR with trimix, drysuit with dry gloves and heating (Finnish divers use argon for the suit). Scooter on the long routes.
- DPV: DPV-suitable
- Essential on the long routes per Sukeltaja-lehti (e.g. 1.7 km continuous at -88 m); in winter you scooter under the ice through the pit.
Who can dive where
- At least Intro to cave
- Configurations: Backmount / twinset / Sidemount / CCR / Small cylinders / no-mount (speleo sumps)
- Goes down to 160 m (trimix or deco may be needed)
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
Only at organised dive events; independent diving is not allowed. Since 26 July 2024 diving is run by Ojamon Kaivossukeltajat ry: membership required, you sign up with your member login. The city of Lohja leases the diving base to a non-commercial diving association; you share the pit with the training institutions Meriturva and Luksia. The older portal ojamodive.fi (Ojamo dive ry) asks you to register with your certifications and lists €10 per dive or €120 per year — check which system applies now. You submit your dive plan to the organiser. Parking next to the pit, heated changing huts; the water is at ground level, so entry is easy. Route: from Kalkkitie turn onto Haikarinkatu, after ~800 m left (old sign 'Ojamon kaivossukeltajat'), after ~100 m left onto the cycle path, gate on the right after ~150 m.
Around Ojamon kalkkikivikaivos (Ojamo)
Fills2 fill stations · nearest 45 km
Varuste.net (Helsinki-Konala)
Malminkartanontie 1, 00390 Helsinki
Air (single and twin cylinders, max 20 l, no composite cylinders) and nitrox (single cylinder); trimix only as part of their tec courses, not as a walk-in fill
Store Mon–Fri 10:00–20:00, Sat and Sun 10:00–18:00 (special hours on the website)
Large outdoor store with a diving department and PADI courses up to Tec Trimix Diver, in Konala in north-west Helsinki. Air €13.90 per cylinder and €18.90 per twinset, nitrox €19.90. Fills are usually done while you wait, but on busy afternoons and early evenings your cylinder may only be ready the next day. Only cylinders with a valid test.
Arctic Divers Dive Center (Helsinki)
Pohjoiskaari 33, 00200 Helsinki
Air to 200 bar (€10–15) and to 300 bar (€10–20); nitrox, O₂ and trimix are not listed — ask
Mon–Fri 14:00–18:00, otherwise by appointment
Dive centre and school in Helsinki; the closest fill station found for visitors. For mixes and CCR gas: ask, or arrange it through your event organiser (Finnish clubs run their own mix stations).
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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 accidents: January 2017 (by then the rescue service had been called out ~20 times for diving rescues there) and January 2026 (diver died during deco in the open pit after a completed dive, at an organised event; cause under investigation). Per Yle, four divers have died at Ojamo in just over 20 years, one of them in the mine area.
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 13 Nov 2026.
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