This is another wonderful seaside running opportunity not far from Dublin. About 1/2 hour by DART from central Dublin, hop off at Salthill & Monkstown station and run along the seaside road and path, past Dún Laoghaire, past the viewpoint at 40 foot (where one can jump off the rocks into the water), and just past the James Joyce Museum to Bullock Harbour. There are water views the whole way, and a seaside walkway/dedicated path for some of it. For the return, you can retrace your steps, or run through the town of Dún Laoghaire and along the R119 main road.
Note: can be windy.