← Dive-sites: Dorothea Quarry £


Dorothea is a large and extremely deep quarry, which is popular among technical divers. After period of closure during 2018, an agreement was arranged that allowed diving for members of the North Wales Technical Divers Club. The club itself was created to allow technical divers to continue using the quarry, and more information can be found by following the link above.

The quarry itself is not only vast, but extremely deep at 104m (depending on who you ask). There are many deep sections with floors at 25, 40m and deeper. Many old huts and quarry workings remain such as cranes, cables and tunnel sections. The car stack (not shown on the maps) is a pile of cars on the west side of the quarry, which have been dumped in and fallen on top of one another – the deeper you go, the older the cars are. Not far from the car stack is a ford escort that seems to stick out of the quarry wall.

Some of the tunnels in the quarry are accessible, and lead through outcrops and ridges. The shallowest section near the car park is useful as a deco loop to swim around in while finishing a dive.

In the summer, the water suffers from severe algae bloom near the surface but this clears up past around 15m. As a result, Dorothea is very dark all year round and other than on the surface, also stays cold throughout. Vis can be incredibly good at depth.

Facilities now include a porta-loo and re-surfaced road, with plans to continue adding to the site (changing room etc.)

Dorothea is surrounded by 4 other quarries, Cloddfar coed Quarry (which can still be dived) as well as Talysarn Quarry, Cornwall Quarry and Twyl Mawr Quarry (in which diving is not permitted).


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Key Metrics

RegionPersonnel AccessRoad AccessDepth (m) *Permission neededLat Long (DD)Elevation (m)
Gwynedd (NW)2/5 Challenging1/5 Difficult104Paid Entry53.055186,-4.240543104

Site Maps


Site Map Courtesy of NWTD

Richard Buftons Map, Circa 1998


(Click the ‘Lat/Long’ data in the ‘Key Metrics’ section for Google Maps directions)
Currently access is only available from the Nantlle Side of the quarry – along the B4418, between Penygroes and Rhyd-Ddu. There is a turn off in Nantlle which takes you west, towards Dorothea. Following the track will lead you to the gate, and after that, the car park.

Additional Risks

  • Extreme Depth
  • Very cold and dark


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