South Wales and Mendip, Great Britain · about 8 km from Abergavenny
Pwll-y-Cwm
- Max depth23 m
- CertificationFull cave
- Water temperature≈ 4–10 °Cestimated, no reports yet
- SpecialSidemount
Diving and fills
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What it looks like
Pwll-y-cwm (South Wales) cave dive on sidemount rebreather 2019 Pwll-y-Cwm to Daren Cilau & back Pwll Y Cwm One Of The Longest Sumps In Wales! - Pwll Y Cwm Sump
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Videos and posts
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Pwll-y-cwm (South Wales) cave dive on sidemount rebreather 2019 Pwll-y-Cwm to Daren Cilau & back Pwll Y Cwm One Of The Longest Sumps In Wales! - Pwll Y Cwm Sump
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Other people's footage, not advice: how someone else dives here says nothing about what suits your team. Dive within your training.
The dive
Pwll-y-Cwm lies in the bed of the River Clydach, where the water of the Llangattock caves returns to daylight.
1 earlier accident or incident has been reported at this cave. Read what happened ↓
Profile and sections
Pwll-y-Cwm lies in the bed of the River Clydach, where the water of the Llangattock caves returns to daylight. The Cambrian Cave Registry calls it an estavelle that gives only divers access to the flooded passages leading to Daren Cilau's terminal sump. Beyond the tight entrance the passage opens up, and you dive on into Daren Cilau, with more than 26 km of passages one of the longest cave systems in the United Kingdom. In the registry's photos the water is clear at normal flow; in flood it wells up red-brown into the river.
In 1986 the CDG linked Daren Cilau's terminal sump by diving to Elm Hole, a rising 60 m upstream of Devil's Bridge. In 1993 a diver got through Pwll-y-Cwm's underwater choke, and in 1994 two divers dived through to Gloom Room Sump in Daren Cilau. According to the registry the spring may also give a way into the main drain of Agen Allwedd, the neighbouring cave system.
- Depth and profile
- After the tight entrance the dive soon drops to ~-23 m, then rises gently over ~650 m into Daren Cilau (UKMC). The Cambrian Cave Registry gives 600 m dived from Daren Cilau's terminal sump to Elm Hole, the neighbouring rising.
- Configuration
- For experienced sidemount divers only (UKMC), so no backmount. The sources do not say whether a sidemount rebreather gets through the tight entrance.
- DPV: Not DPV-suitable (estimate)
- Tight entrance against the flow and sidemount only: no gain.
Who can dive where
- At least Full cave
- Configurations: Sidemount / CCR
- Goes down to 23 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
A short walk from the road (UKMC). The spring lies in the bed of the River Clydach, near Elm Hole in the Clydach Gorge (Cambrian Cave Registry). The sources give no access rules: check the current arrangements with the CDG (Welsh Section).
Around Pwll-y-Cwm
FillsNo fill station known nearby
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Other sites5 within 59 km
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 diving accident at Pwll-y-Cwm in April 2011.
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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