The Blue Lagoon at Abereiddi: How to Visit, Swim and Stay Safe

The Blue Lagoon is what happens when the sea breaks into an abandoned slate quarry and a century of minerals turns the water an implausible blue-green. It sits just north of Abereiddi beach on the St Davids peninsula, ringed by ruined quarry buildings, deep enough that Red Bull's Cliff Diving World Series used it as a venue — and it has become one of the most photographed places in Wales. Here's how to visit it well.

Getting there and parking

Park at Abereiddi, in the car park behind the pebble beach at the end of the lane from Croesgoch (charges apply in season, and it fills early on fine summer days — this is a small cove with one car park, not an attraction with an overflow field). From the car park it's a five-to-ten-minute walk north along the obvious coast path over the little headland, and the lagoon opens below you. Sturdy footwear beats flip-flops: the paths are quarry rubble.

No facilities at the lagoon itself — Abereiddi has seasonal basics at best, so the nearest reliable food, toilets and a proper pint are a mile up the coast path at Porthgain, home of The Sloop Inn and The Shed.

Why it's that colour, and how deep it is

It's a drowned slate quarry — worked until the early twentieth century, then breached to the sea through the narrow gap you can still see. The colour is minerals in the slate, not tropical warmth: this is cold, deep water (around 25 metres in the middle) even in August, and it stays cold below the surface layer all summer.

Swimming and jumping, honestly

Swimming here on a calm day is glorious — sheltered, clear, and unlike anywhere else in Wales. The honesty:

No lifeguards, ever. Cold, deep water saps swimmers faster than they expect; the cold-shock advice on our wild swimming guide applies double here. Get in gradually, stay near the edges until you know how you're coping, and never swim through the seaward gap when there's any swell running.

The jumping is the famous bit — do it with the professionals. The quarry walls and the old buildings are why coasteering was practically invented on this coast, and guided groups jump here every day of the season with wetsuits, buoyancy aids, helmets and guides who know today's water level and today's swell. Celtic Quest run sessions at Abereiddi itself, and our coasteering guide covers the rest — including two Tenby-based sessions you can book online. Unguided jumping from the high walls into water you haven't checked has hurt people here. The ruin walls are also just that — century-old ruins; don't climb them for a photo.

Winter storms rearrange the coast. Out of season, swell surges through the gap and the lagoon stops being a lagoon and becomes a funnel. A calm summer evening and a February gale are different places.

Make the day of it

The Blue Lagoon is twenty minutes of wonder unless you swim — so build the day around it. The classic: lagoon first thing (before the car park and the crowds), then the coast path mile to Porthgain for lunch, with Traeth Llyfn — a wild, cliff-stairs-only sandy beach — as the detour between them. That whole stretch is part of one of the finest Coast Path stages in the county. St Davids and Whitesands fill the afternoon, and our St Davids area guide has the where-to-stay picture if one day isn't enough — it rarely is.