A major search took place on Monday after reports of a capsized boat off the coast of Co Antrim.
A number of lifeboats attended the incident close to Larne, with the Coastguard helicopter also attending.
An RNLI spokesperson said: “Larne and Red Bay RNLI’s all-weather lifeboats launched this afternoon following a report of an upturned catamaran approximately 12 miles from Larne.
“The Coastguard helicopter from Prestwick has also been tasked and two P&O ferries in the area are also assisting. The operation is ongoing.”
HM Coastguard said helicopters from Prestwick and Larne and Red Bay RNLI lifeboats were tasked to the scene after a report of the overturned craft was received at around 4.20pm.
P&O Ferries European Highlander and European Causeway had earlier assisted with the search before making their way to their final destinations of Larne and Cairnryan respectively.
It is understood both vessels used thermal imaging cameras to help search teams in the area.
Weather conditions in the area had been foggy at the time the incident was reported, with rain and wind also causing difficulties for the search teams.
Alliance Party MLA for East Antrim, Danny Donnelly, said the news was “incredibly concerning”.
“My thoughts are with those involved. I hope they are rescued and brought ashore by the lifeboat services,” he posted on X.