← Dive-sites: Llyn Cwellyn


Llyn Cwellyn is a reservoir with easy access, good parking and a nice shallow entry point on the east side, which lies to the west of Mt. Snowdon. It has a very silty bottom which after a shallow plateau, drops steadily to its deepest point of 37m (although I’ve only been able to find 32m). There’s not really anything to see and it gets pretty dark towards the bottom. Very similar to Coniston Water.

The reservoir is home to Arctic Char, Brown Trout. Engines are not permitted so you should be fine without an SMB providing there are no boats on the water (I’ve never seen any). Wind coming down through the valley could be an issue if you surface in the middle so plan to return where you went in – there is only only really one area to get out with access to the car park.

The car park, just off the A4085 is something like £4 for the day and has portaloos. It makes for very easy to waters edge and there are even a few benches nearby for lunch if the weather’s good.


Cwellyn from the shore

Cwellyn from the shore

Key Metrics

RegionPersonnel AccessRoad AccessDepth (m) *Permission neededLat Long (DD)Elevation (m)
Gwynedd (NW)5/5 Excellent5/5 Excellent37Unknown53.072554,-4.149445214



©OpenStreetMap contributors


By road – Llyn Cwellyn lies about 7 miles from Caernarfon and 1.5 miles from Rhyd Ddu, along the A4085. The easiest access point is the National Park Authority Car Park, across the road from the YHA Snowdon Ranger hostel.
To the water – at the edge of the top side of the car park is a footpath, through some woods which leads to the waters edge. Not far through, the path splits in three directions. The left takes you up to the YHA Snowdon Ranger hostel, the right takes you to entry point A and straight ahead takes you to entry point B.
Entry point A – Heading to A will take you to a nice rocky shore, which is probably the easiest place to enter the water.
Entry point B – Point B is along a wooden walkway with a picnic bench at the end. You can drop of the edge to get to the shoreline.


  • The Lakes of Eryri by Geraint Roberts. Gwasg Carreg Gwalch, Llanrwst, 1995.
  • ©OpenStreetMap contributors

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