An Elizabethan cannon caught Simon Cosbey's eye on a day out at a museum in the Republic of Ireland.
There was something very familiar about it.
When he read the text beside it, he said, "it all fell into place".
The bronze cannon he was looking at was the very same one he had helped haul off the seabed near Larne, County Antrim, three decades before.
In the 1980s Mr Cosbey was a keen diver with a club in Castlereagh, County Down.
He went on a routine dive looking for salvage - the idea was to sell what the group found and make some money for the BSAC (British Sub-Aqua Club).
The group headed north from Castlereagh and started scouring Larne Lough, 100 yards out from Ballylumford power station.
Bu Mr Cosbey and his fellow divers found more than they bargained for.
On the seabed that day in 1985, they found two 16th Century cannon emblazoned with the Tudor rose.
Each one weighed three-quarters of a ton.
The divers took the next day off from their jobs and, in a team of ten, set to work.
They raised the cannon by ropes after pumping air into lifting bags, then they towed them in to shore.
It was not meticulously planned out, Mr Cosbey admitted.
"Looking back I am amazed we managed to bring them to the surface," he said.
It was while the group was dragging the cannon on to the beach that it became clear just how old the cannon were.
The cannon bore a Tudor Rose motif and the date 1559 was written on the side.
It is still not known how they came to be on the north-western end of the Irish Sea.
They may have been ballast, thrown overboard to dislodge a grounded ship, said Randal Armstrong, a former chairman of the Castlereagh diving club.
He offered another explanation - the cannon might have been on their way to be used at fortifications on the Irish coast when a boat they were on sank.
The cannon were sold and the club used its £13,000 fee to buy a clubhouse for meetings and events.
"Any amateur club would be delighted with an influx of money like that," Mr Cosbey said.
"It was serendipity we found something of that magnitude - we had only gone down to look for scrap metal because it was an old anchorage."
The cannon went into storage at the Ulster Museum but were never put on show there.
Many objects are held in storage because of limits on display space.
But now, nearly 30 years after the find and years since he had all but stopped diving, Simon Cosbey was looking at one of the cannon at the Battle of the Boyne visitor centre near Drogheda.
The centre has the cannon on loan from the Ulster Museum. All its other cannon are replicas.
Mr Cosbey brought the original club members to see the cannon on display, and they also visited the second cannon in its Ulster Museum storage space.
The chief executive of BSAC said the cannon were "just a perfect example" of the "fascinating finds" divers can come across.
"Our club divers are passionate about diving and the wonderful experiences it can give you," Mary Tetley said.
The episode has not convinced Mr Cosbey to go back to diving. His son, however, has become the thrill-chaser of the family: he sky-dives as well as being a scuba diver.