Cave and mine diving in South Wales and Mendip
Caves and mines between the Brecon Beacons and the Mendip Hills: the shallow sumps of Porth yr Ogof, the freely accessible Dinas silica mine, the deep Noxon Park iron mine in the Forest of Dean (via the local access agreement) and Wookey Hole, the birthplace of cave diving (only via the CDG).
4 sites · down to 90 m · 2 suitable for an intro team
All 4 sites
| Site | Max depth | Type | Certification |
|---|---|---|---|
| Dinas Silica Mine (Upper Dinas) | 22 m | Backmount | Intro to cave |
| Noxon Park Iron Mine | 50 m | Sidemount | Full cave |
| Porth yr Ogof | 7 m | Sidemount | Intro to cave |
| Wookey Hole | 90 m | Sidemount | Full cave |
Certification requirements, configurations and trimix depths are estimates for planning. Always check them locally and dive within your training.
Practical info: rules, fills and emergency numbers
Emergencies
- 999 or 112. Accident in a cave or mine: call 999, ask for the police and say it is a cave rescue. Diving accident on land: National Diving Accident Helpline 07831 151 523 (24 h, England and Wales) or the nearest BHA chamber; DAN Europe +39 06 4211 5685.
- Chambers (the BHA list has none in Wales): DDRC Healthcare, Plymouth Science Park, Research Way, Derriford, Plymouth PL6 8BU, tel. 01752 209999, category 1 (~2 h 30 from Chepstow). Midlands Diving Chamber, Hospital of St Cross, Barby Road, Rugby CV22 5PX, tel. 01788 579555, emergency 07931 472602, category 2: no critically ill patients (~2 h).
Access and rules
- Access: almost all British cave-diving sites are on private land and you need the owner's permission; the Cave Diving Group (CDG) knows the current arrangements. One careless visit can close a site for everyone.
- CDG: the British cave-diving club, with a Somerset Section and a Welsh Section. Overseas cave divers can only get temporary membership; details via the CDG. Wookey Hole is only via the CDG; Porth yr Ogof, Dinas and Noxon Park can be dived without the CDG.
- Insurance: BCA membership (caving member £32 a year) includes public liability insurance. FoDCCAG issues Forest of Dean permits to BCA members only (permits@fodccag.org.uk).
Gas and fills
- Gas: Vobster Quay (air, nitrox, trimix, O₂; max 232 bar) and Cardiff Scuba in Dinas Powys (air to 300 bar, nitrox up to 99 %, trimix with at least 3 hours' notice). No trimix fill station is known in the Neath valley itself: bring O₂ and diluent.
Water and season
- Water and visibility: in sumps rarely above 7 °C and often around 4 °C, with 1–2 m visibility normal and 3–4 m exceptional (CDG); InDEPTH gives an average of 7–10 °C. The Dinas and Noxon Park mines are ~7 °C with usually (very) good visibility.
- Floods: Porth yr Ogof turns into a raging river after rain; in Wookey Hole floods leave debris, buried lines and silt banks.
Safety
- British practice: the CDG recommends solo diving in British sumps because no British sump allows unimpeded buddy diving; expect many branch lines (in one example 10 in the first 500 m). Sidemount, helmet, hand-held lights and permanent 4 mm lines are the norm.
Rest day
- Non-diving day: Porth yr Ogof is also a popular dry caving trip (over 30,000 visitors a year) and Wookey Hole is a show cave.
Good to know
- Inland dive centres: NDAC near Chepstow closed permanently on 18 February 2022; the NDAC quarry near Ammanford (124 m deep) is for training organisations only. Vobster Quay (Somerset) is an open quarry to -36 m, members only; non-members on Tuesdays 08:00–15:00 after registering.
Plan a cave diving trip to South Wales and Mendip
Enter your team, with certifications, gas and configurations, and see right away which caves fit. With driving times from your stay, fill stations and an AI instructor who thinks along.
Compiled from public sources (Cave Diving Group, InDEPTH 2020–2021, TDI/Scubaverse 2019–2021, UKMC, ogof.org.uk, Brecon Beacons National Park Authority 2009, Wikipedia, aditnow, Coflein, Natural Amenities Ltd, cave-dive-make, FoDCCAG, mindat, Martyn Farr/Vertebrate 2024, British Caving Association, British Hyperbaric Association, DDRC, NDAC, divernet, Vobster Quay and Cardiff Scuba; Sept 2026). Pins converted from grid references (ogof.org.uk, aditnow, mindat) or taken from Wikipedia; the Noxon Park pin is accurate to ~100 m. ~ = estimate. Access and rules change — check locally.