Blue Lagoon, Abereiddi

The Blue Lagoon is a flooded slate quarry just north of Abereiddi beach, opened to the sea when its channel was blasted; the slate gives the deep water its blue-green colour. It is busy with coasteering and kayak groups in summer, and there are no lifeguards. The National Trust closes the lagoon each autumn while grey seals are pupping, so check before you travel.

Directions

Photo: August Schwerdfeger · CC BY 4.0

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Latest reading · SwimScore 76/100 (Good swim) for a typical swimmer: air 12°C, wind 11 km/h, waves 0.8 m, UV 0. Updated 23 Sept, 22:00 UTC.

Know before you go

Getting in: Owned by the National Trust. A wheelchair-accessible path leads north from the beach to the lagoon, past ruined quarry buildings and workers' cottages. The lagoon (and nearby Traeth Llyfn) is closed each autumn to protect grey seals and their pups: 21 September to 7 November in 2026.
Parking & transport: Privately owned field car park at the top of the hill down to Abereiddi, with seasonal charges; very limited disabled parking next to the beach. The Strumble Shuttle coastal bus stops at Abereiddi.
Lifeguards: No lifeguards at Abereiddi.
Water quality: The adjoining beach, Abereiddy, is a designated bathing water classified Excellent in 2025 (Welsh Government / Natural Resources Wales).
Season: Busiest in summer; closed to visitors each autumn during the grey seal pupping season.
Who swims here: A regular venue for guided coasteering, and a stage of the Red Bull Cliff Diving World Series in 2012, 2013 and 2016.
Watch for: Deep water: about 25 m according to a national park information board
Currents and undertows in places when bathing at Abereiddi
Unsupervised cliff jumping ('tombstoning') is extremely dangerous; coasteering should be done with a qualified provider
Facilities: Toilets (seasonal; opening dates set by Pembrokeshire County Council) · Mobile refreshment kiosk visits the car park · No litter or dog bins