Overview
Half Moon Bay is not a bay and there is no sand. It is a bathing spot on the south side of the Great South Wall, on the walk towards the Poolbeg lighthouse, with ladder and slipway access into the Irish Sea. The wall is exposed to wind and waves. Check Dublin Port notices before setting out, and turn back if waves are breaking over the wall.
The swim
Water access is by ladder or slipway. Follow any posted instructions, and leave club facilities and gates clear; they are not for general use. For a walk, keep to the public route along the wall.
The water stays cool the year round, so a wetsuit is worth it for anything more than a quick plunge. Tides make a real difference to the depth, so check a tide chart first. Currents can run strong, so swim with someone, especially in winter, and heed the safety notices from Dublin Port Company, which can close the area in severe weather or during port operations.
Water quality
Dublin City Council monitors water quality at Half Moon. Check the latest EPA listing and any bathing advisories before you swim. Heavy rain can affect bathing water in the days afterwards, so follow the advice in the current notices rather than any rating you may have seen earlier.
History
The Great South Wall was finished in 1795, built to stop Dublin Port silting up and to give ships a safe anchorage. The Half Moon swimming and water polo club has been linked with this spot since 1898, and its clubhouse on the wall started life as a station for an army gun battery guarding the port. The outlook has not changed much: Dublin Port working away on one side, the Poolbeg lighthouse ahead, and the open Irish Sea beyond.
Wildlife
The wall runs along the edge of South Dublin Bay, a protected area for wintering birds, so there is usually something to watch on the mudflats at low tide, including ducks, waders and gulls through the colder months. Early morning is the quietest time.
Getting there
Half Moon Bay sits along the Great South Wall, so however you come, there is a walk, and the route is exposed in poor weather. The DART stations are a good way off in the city, leaving a long onward hop by bus, bike or taxi. Give way to walkers on the wall, and check the tide and the port and bathing notices before you set out. Bring everything you need, as you should not count on shops or cafés near the end of the wall.