A search operation was carried out after the coastguard received reports of a man going overboard from a passenger ferry which was on the way to Co Antrim yesterday.
The UK Coastguard said crews responded to the incident on the Stranraer to Larne service at 1.21pm.
They said Larne and Portmuck Coastguard rescue teams, RNLI lifeboats from Larne and Donaghadee and an coastguard rescue helicopter took part in the operation.
P&O Ferries confirmed an incident occurred onboard the European Highlander ferry while it was sailing to Larne.
It said: "We are working closely with the relevant authorities, who are actively responding.
"Our priority is the safety and wellbeing of all involved, and we will provide further updates as more information becomes available."
