An operation to recover the body of a diver who died while trying to assess the chances of recovering a sunken German U-boat is to take place later.
Michael Hanrahan died during the dive to the U-boat
Michael Hanrahan, a father of four from Dublin, died during a dive at the sunken submarine, 16 miles off Malin Head on the Donegal coast, on Tuesday.
The dive team was filming the U-boat when the diver got into difficulties.
Other members of the team tried to help him - but they were unsuccessful. It is not clear what led to the accident.
Later on Wednesday, a team will attempt to recover the body.
Paul Moore, from BBC Radio Ulster's Your Place and Mine, spent Tuesday with the divers at Malin Head, for a feature he was doing for the programme.
"It was just such a huge shock, because they were just so excited about it and they seemed to know just what they were doing," Mr Moore said.
"It's just such a tragedy for the family."
He said later he was looking at photographs he had taken of the divers.
"I was looking at these photographs and realising that one of these divers was still there, had had this accident and was now dead," he said.
"Four hours earlier I had been talking to these guys - just four typical guys just loving what they were doing."
Derry City councillor Shaun Gallagher paid tribute to Mr Hanrahan.
"He was a gentle giant and a lovely man - we're just devastated," he said.
The dive team leaving for the U-boat site on Tuesday
It is the second fatal diving incident off the north-west coast in the last two months.
At the end of July, Paul Jackson, a police officer from Humberside, had been looking at wrecks off Tory Island but failed to resurface.
The U-boat, which did not see any war action, sank while being towed from Scotland to Londonderry to be scrapped.
Derry City Council plans to raise U-778 and house it in a museum. The boat is lying in about 70 metres of water.
It is estimated there are about 150 such boats lying off Malin Head, all vivid reminders of the Battle of the Atlantic during World War II.
The council said that "because of the depth of the waters involved, the procedure was expected to be highly technical".