The body of a woman in her 50s was recovered from Carlingford Lough in the early hours of Friday morning.
The alarm was raised on Thursday night after a report that a car had gone off the pier at Narrow Water.
Following a search by gardaí (Irish police), the Irish Coast Guard and Kilkeel RNLI, the body and a car were found near Narrow Water, County Louth.
On the Warrenpoint side of the river, the search was conducted by PSNI and HM Coastguard.
Gardaí said the incident is "being treated as a personal tragedy".