According to official records, the German U-boat was simply a casualty of the First World War – scuttled after her crew surrendered.
However, the legend of UB-85 tells a different tale of a huge sea monster with glistening teeth and large eyes.
Now, almost a century after the boat vanished beneath the waves, marine engineers believe they may have stumbled across the 148ft wreck off Stranraer, Wigtownshire.
They made the discovery while preparing to lay cables under the Irish Sea in ScottishPower and National Grid’s £1billion Western Link project.
Innes McCartney, a historian and nautical archaeologist trying to identify the vessel, believes the riddle of the sea monster could now be unravelled.
Dr McCartney said: ‘In the waters of the Irish Sea there are at least 12 British and German submarines known to have sunk.
‘The features of this wreck, largely intact, confirm it as a UBIII-class submarine, of which we know of two lost in the area – the more famous UB-85 and its sister boat UB-82.’
He continued: ‘Unless a diver can find a shipyard stamp, we cannot say definitively – but yes, we’re certainly closer to solving the so-called mystery of UB-85 and the reason behind its sinking – whether mechanical failure or something that is less easily explained.’
Official reports from the time tell how the submarine was caught on the surface on April 30, 1918, by patrol boat HMS Coreopsis.
The Germans surrendered without resistance, much to the surprise of the British, who then sank UB-85.
But rumours quickly surfaced of a sea creature terrorising the German crew.
According to folklore, when the commanding officer was questioned why he had been cruising on the surface he revealed an astonishing encounter with a creature from the deep.
Captain lieutenant Günther Krech told how the U-boat had been recharging batteries at night when the beast emerged from the sea.
It is claimed he described a creature with ‘large eyes, set in a horny sort of skull’ and ‘teeth seen glistening in the moonlight’. Startled, his men began firing at the monster which refused to let go of the forward gun mount.
As the vessel began to list, the captain ordered his men to continue the attack until the monster finally slipped back under the water.
Shaken but unharmed, the crew quickly realised the boat was badly damaged and unable to submerge. The captain is said to have told the British: ‘That is why you were able to catch us on the surface.’
Gary Campbell, keeper of the Loch Ness Monster official sightings register, believes there could be some truth in the incredible tale.
‘The WWI report from the captain of the British ship HMS Hilary a year earlier makes it clear that seafarers were well aware of large sea “monsters” that could harm their ships.’
The area where the U-boat sank had a history of sea monster sightings.
ScottishPower’s Peter Roper said: ‘The images from the subsea scans are incredibly detailed, but we need to be aware of what lies beneath. In all the years I have been building power lines, this is the most extraordinary discovery.’