Cwmystradllyn is Pwllheli & District's headline stillwater, a reservoir on the Llŷn side of the Snowdonia boundary stocked with rainbows and blue trout over a base of wild browns — a more varied bag than most of the small upland llyns manage. The club keeps its site current, which is more than can be said for some of the region's waters, and Cwmystradllyn benefits from it: better information, a clearer stocking picture, and a reputation as the association's most reliable sport. It sits in the Dwyfor catchment on the quieter, western edge of the mountains, away from the Snowdon crowds, and gives the Llŷn Peninsula's anglers a genuine stillwater option without having to cross into Eryri proper for it.
- Lake
- Ordovician volcanics