THE scuttled Second World War U-boat at the bottom of Lough Foyle has turned out to be a sonic illusion.
A team from Mallow, Co Cork, using sonar equipment came across what they believed to be a wreck on the lough bed near Derry.
The Cork search and rescue unit was asked by the Royal Navy and authorities to conduct more detailed scans on the wreck site to identify the mystery object.
But the outline of what they thought was a rare German submarine was just an illusion.
Northern Ireland Environment Minister Alex Attwood had called in marine experts to check if the outline was a submerged submarine.
A series of sonar surveys were made across the lough, which was one of the most important naval bases during World War II.
Unfortunately, when the site was scoped out the sonar exaggerated and enlarged whatever was there.
"There is no doubt for a moment there was a thrilling possibility which has now not come to pass. I do share a sense of disappointment," said Mr Attwood.