The northern half of Wales has numerous lakes and other places suitable for swimming. Generally, swimming is allowed in most natural lakes, but not in working reservoirs. Welsh lakes can be classed as either oligotrophic or mesotrophic. Oligotrophic lakes are low in nutrients, and therefore have little or no algal growth. This makes entry easier as the bottom isn't slippery. Such lakes are usually found high in the mountains. Mesotrophic lakes are found lower in the valleys, and often have considerable algae growth on the bottom, as well as various water-weeds.
Safety : lakes are not swimming pools; the water will be cold, you may swim into water weeds or if the lake has wooded sides, there may be tree branches in the water. Power-boats are allowed on Bala Lake, Llyn Geirionnydd and Llangorse Lake, so on these ensure that you are clearly visible. It's always best to swim with a companion, but if that's not possible, take a tow float. Always swim within your ability and don't be tempted to swim too far from the banks unless you're a competant swimmer. Also, beware of blue-green algae in summer.

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Lakes in Alphabetical Order

Lakes listed from North to South

Ffynnon Lloer
Ffynnon Lloer
A good size lake high up in the Carneddau range.
Llyn Geirionydd
Llyn Geirionydd
A popular woodland lake with parking.
Llyn Idwal
Llyn Idwal
A popular lake for swimming, just over ½ mile from the A470.
Llyn Bochlwyd
Llyn Bochlwyd
At a height of 1820 feet, this lake is alongside the path up Glyder Fach.
Llynnau Mymbyr
Llynnau Mymbyr
Two good lakes for swimming and watersports - just west of Capel Curig.
Llyn Cwmffynnon
Llyn Cwmffynnon
A good-size moorland lake on the opposite side of Pen-y-Pass from Snowdon.
Moel Siabod Quarry Lake
Moel Siabod Quarry Lake
A deep quarry lake on Moel Siabod.
Llyn y Foel
Llyn y Foel
A shallow lake part-way up Moel Siabod.
Llyn Llydaw
Llyn Llydaw
A good lake for swimming, part-way up Snowdon.
Glaslyn (Snowdon)
Glaslyn (Snowdon)
A deep corrie lake on the path up Snowdon. Crystal clear water.
Llyn Gwynant
Llyn Gwynant
A large lake good for swimming, easily accessed from the A498.
Bala Lake
Prince of Wales Reservoir
A small lake, formerly a reservoir at the head of the Cwm Pennant valley.
Llyn Dinas
Llyn Dinas
A good lake for swimming, easy access from the A498.
Llyn Llagi
Llyn Llagi
A circular moorland lake.
Llyn yr Adar
Llyn yr Adar
A peaty moorland lake at about 1800 feet with a small rocky islet in the centre.
Llynnau Cerrig-y-myllt
Llynnau Cerrig-y-myllt
Two small lakes high up on the slopes of Cnicht.
Llyn Newydd
Llyn Newydd & Llyn Bowydd
Two former reservoirs above Blaenau Ffestiniog.
Llyn Cwm corsiog
Llyn Cwm Corsiog & Llyn Clogwyn brith
Two former reservoirs, high up in the mountains above Blaenau Ffestiniog.
Llyn Cwmorthin
Llyn Cwmorthin
A good lake for swimming, near Blaenau Ffestiniog.
Llyn Du Bach
Llyn Du Bâch
A small lake above Blaenau Ffestiniog.
Llyn y Manod
Llyn y Manod
A good- lake for swimming between Manod Bach and Manod Mawr.
Llyn Mair
Llyn Mair
A small lake alongside the B4410 with parking and picnic area.
Rhaeadr Ddu
Rhaeadr Ddu
A waterfall and plunge pool in a wooded valley west of Trawsfynydd.
Llyn Hiraethlyn
Llyn Hiraethlyn
A moorland lake east of Blaenau Ffestiniog.
Bala Lake
Bala Lake
Wales' largest lake - 4 miles long and ½ mile wide. Good beach area and facilities.
Llyn Eiddew bach
Llyn Eiddiw bach
A small lake alongside the track up to Moel Ysgyfarnogod.
Llyn Eiddew mawr
Llyn Eiddiw mawr
A large moorland lake in the Rhinog mountains.
Bala Lake - Llangower
Bala Lake - Llangower
The western end of Bala lake, next to Bala Lake Railway Llangower station.
Llyn Cwm Bychan
Llyn Cwm Bychan
A scenic lake about 5 miles from Llanbedr. Good base for walking.
Llyn Morwynion
Llyn Morwynion
A natural lake in the Rhinog mountains near the Roman Steps. Now used as a reservoir.
Gloyw Llyn
Gloyw Llyn
An 8 acre natural lake in the Rhinog mountains north of Rhinog Fawr.
Llyn Du
Llyn Du
A small lake north of Rhinog Mawr near the Roman Steps.
Llyn Perfeddau
Llyn Perfeddau
A small lake in the Rhinogydd range at a height of 1530 feet, east of Llanbedr
Llyn Irddyn
Llyn Irddyn
A clear moorland lake on very rough ground, east of Tal-y-Bont.
Pont Llanelltyd
Pont Llanelltyd
A popular swim spot, just off the A496 near Dolgellau. A good place to stop for a break on a hot day.
Llyn-y-Gadair
Llyn-y-Gadair
An oligotrophic lake high up on the Foxes' path up Cadair Idris.
Llyn Gafr
Llyn Gafr
A small lake on the Foxes' path up Cadair Idris.
Fairbourne Blue Lake
Fairbourne Blue Lake
An abandoned quarry lake, very popular for swimming. Entrance is via a short tunnel.
Llyn Cau
Llyn Cau
A very deep, circular lake at about 1500 feet up Cadair Idris.
Tal-y-Llyn
Tal-y-Llyn
A long, but shallow lake beneath Cadair Idris. Parking available in laybys.
Teifi Pools
Teifi Pools
Six small lakes - three of which are used as reservoirs - about 20 miles east of Aberystwyth.
Rosebush Quarry
Rosebush Quarry
A small quarry lake in mid-Pembrokeshire, on the side of Foel Cwmcerwyn.
Blue Lagoon, Abereiddy
Blue Lagoon, Abereiddy
A former slate quarry, connected to the sea and flooded with jumps from the rocks above.
Keepers Pond
Keepers Pond, Blaenavon
A small pond, alongside the B4246 north of Blaenavon.