At approximately 10pm on Tuesday night, gardaí and emergency services rushed to the scene having received reports of a man entering the water.
The body of a man in his 40s was retrieved from the water and brought to St. Vincent's Hospital, where he was officially pronounced dead.
A post mortem will take place in the coming days.
Gardaí are not treating the incident as suspicious.
"Gardaí and emergency services attended Dun Laoghaire yesterday evening Tuesday 17th August 2021," a garda spokesperson said. "A male aged in his 40s was recovered from the water and taken to St Vincent’s Hospital where he was pronounced deceased. A post mortem will take place in due course. Investigations are ongoing."
