The Irish coastguard joined in with a search for a missing diver off Rathlin Island on Sunday.
It sent a helicopter from Sligo to assist the RNLI in the hunt for the man, who had gone missing before 12.25pm while diving at a wreck on the east side of the island.
RNLI crews from Scotland, as well as local boats from Ballycastle, also came to assist the local RNLI team before the man was discovered after two hours, roughly four miles from his original position.
He was taken to Craigavon Area Hospital.
His condition is stable.
Speaking following the call out, Portrush RNLI Coxswain Des Austin said: “We are so relieved this afternoon that after almost two hours of searching the diver has been located safe and well.
“This was a multi-agency search and rescue effort where the emergency services were assisted greatly by a number of local vessels. “I would like to commend the diving party for raising the alarm as soon as they noticed one of their group had gone missing and praise the community effort that ensured this man was brought safely back to shore.”