Glendalough National Park Swim — May

The Glendalough National Park Swim is one of Ireland's most popular open water events, set in the stunning Upper Lake of Glendalough in the Wicklow Mountains. The May 2026 edition on 9 May offers a 1,500m course through glacial waters surrounded by ancient monastic ruins and steep valley walls. Organised by Open Water Swimmer Ireland, the event has sold out every year since its inception — early registration is essential.

Glendalough Upper Lake is a glacial lake at altitude, which means the water is cold year-round. In early May, expect temperatures around 10–12°C. The lake is relatively sheltered by the valley walls, so wind chop is less of a factor than on exposed lakes, but visibility in the dark peaty water is low — you're swimming by feel and sighting off the mountains. Wetsuits are strongly recommended but not compulsory — you can swim skins if you choose. The 1,500m course is a loop in the Upper Lake. The setting is genuinely special: you swim beneath the cliffs with the Round Tower visible on the hillside. It feels remote despite being just over an hour from Dublin.

Registration opens 14 April 2026 through openwaterswimmer.ie. Entry is €55. The event sells out quickly every year — in some years within hours of opening. Set a reminder for the registration date and be ready to book the moment it goes live. There are no on-the-day entries. No Swim Ireland membership is required.

Glendalough is in the Wicklow Mountains, roughly 1 hour 15 minutes from Dublin city centre via the N11 and R755. The Upper Lake car park is a short walk from the start area, but parking is limited — arrive early. Glendalough village has a hotel and a few B&Bs, but most swimmers drive from Dublin or stay in Laragh (2 min away) or Rathdrum (15 min). The Wicklow Way passes directly through, so there are several hostels and guesthouses in the valley.

Glendalough hosts a second, larger swim weekend in September with 750m, 1.5km, and 3.9km distances — a good step up if you complete the May event. The Malahide Friday Night Swim Series (May–June) offers a more accessible entry point to open water if you're building towards Glendalough. For a very different open water experience, the Gaelforce Great River Swim (May) runs on the same weekend in the midlands.