A man, 45, has died while diving near Roches Point at the entrance to Cork Harbour.
The alarm was raised after the man surfaced to his boat following a dive.
Members of Crosshaven RNLI lifeboat crew rendered first aid and the man was taken ashore and brought to Cork University Hospital.
He was pronounced dead there later.
The man is understood to have been from Co Limerick, where he was a member of a voluntary divers search and rescue unit in North Cork.
A post-mortem examination will be conducted later.