The Dún Laoghaire Harbour Race along with the Dublin City Liffey Swim are rightly considered the two most prestigious swimming races on the Leinster Open Sea calendar. For swimmers, winning the Dún Laoghaire Harbour Race is akin to winning an All-Ireland Final. Sea swimmers aim to win one of the big two over their career.

The race caters for swimmers as young as 14 years of age, up to senior citizens. There are also two children's races of 100 metres and 200 metres, for children 13 years of age and younger, which are held before the men's race. As this is a handicapped race, every swimmer has a chance of winning so you don't have to be a former Olympian to compete or win.

The course comprises a 2,200 metre race along the circumference of Dún Laoghaire Harbour, battling fellow swimmers, reaching marker buoys, avoiding any number of obstacles and taking on the might that is the Irish Sea. The race starts at the RNLI slipway beside the East Pier. The Swimmers then swim out by the National Yacht Club of Ireland, the RNLI lifeboat and out along the Carlisle Pier. They from there to the mouth of the Harbour and the East Pier Lighthouse. This is roughly the half way point. Friends, family and spectators then can walk or run along the East Pier and follow the swimmers as they battle the last 1,000 metres home, past the anemometer, the Boyd Memorial, the Band Stand and finally the last gruelling two hundred metres from Berth No 1 back to the finish line at the RNLI slipway.