The quarry ceased operations in 1910 when the sea breached the outer wall, flooding the workings.
The water depth in the lagoon reaches approximately 25 meters in certain sections.
The site was historically part of the St Bride's Slate and Slab Company.
The lagoon is a designated Marine Special Area of Conservation, hosting diverse marine life in its deeper waters.
The Blue Lagoon at Abereiddi is a flooded former slate quarry located on the Pembrokeshire coast. The striking turquoise color of the water is caused by the depth of the flooded pit and the presence of minerals from the slate workings. Originally connected to the sea by a narrow channel, the quarry provided slate for roof tiles exported from the adjacent beach. It is currently managed by the National Trust and is a destination for coasteering and cliff jumping. The jagged, dark slate walls contrast sharply with the deep blue water, creating a distinct geological landscape. Visitors access the lagoon via the Pembrokeshire Coast Path. The site is part of a wider coastal region encompassing the fossil-rich cliffs of Abermawr.
From the high ridge on the northern side of the quarry, looking down into the basin towards the sea channel.
Wear sturdy footwear as the path around the quarry and the descent to the water are uneven and rocky.
Bring a wetsuit if you plan on swimming, as the deep water remains very cold even in mid-summer.
Check local tide charts before visiting to see the state of the beach and the channel area.
Do not attempt to jump from the highest points if you are not an experienced coasteerer, as submerged debris remains from the mining era.
Respect the environment by removing all litter; cliff jumping is inherently risky and performed at your own peril.
