IT was saved from the scrap after being bought for less than £1 and now a unique piece of Second World War history is being restored with the help of a Poulton company.
The German vessel U-534 was sunk between Denmark and Sweden after being attacked by the RAF in 1945.
After being discovered by a Danish diver the submarine was given a new lease of life when it was raised from the sea bed 15 years ago.
But disaster struck again and it appeared destined for scrap after the Historic Warships collection in Birkenhead, where it was housed, closed.
That was until Merseytravel pledged to restore the submarine to its former glory after buying it from its Danish owners for 1 two years ago.
A team of engineers at Poulton-based BSA – which normally manufactures recycling equipment – have now been contracted to realign the guns.
Steve Mattinson, director of BSA, on Bracewell Avenue, said: "It's the gun off a German sub which has been cut up into different sections.
It's got a slight bend on it which we are trying to straighten.
"It's well rusted but a lot of the parts are still very well greased up so we are hoping everything will work. It's in quite good condition considering it's been under water for about 40 years."
The engineers began steam cleaning the gun to get rid of layers of sand and silt.
Mr Mattinson added: "We've got pull lifts on it, there's a lot of weight on it to try and unlock the guns and get them to move.
"We normally manufacture recycling equipment so this is a bit different.
"It's a bit of a challenge, but we've been engineers a long time and this is just another piece of equipment.
"We've had people coming in to have a look and have their photo taken next to it. I guess it's a bit of a souvenir.
"It'll never work again, you'll have to be a brave man to try it!"
The U-boat is set to become a major tourist attraction depicting the history of undersea warfare at Mersey Ferries' Woodside Ferry Terminal, in Birkenhead, next year.
Neil Scales, chief executive and director general of Merseytravel, which owns and operates Mersey Ferries, said:"More people than ever before will be able to view the sub in its new location.
"Previously youngsters under the age of 16 were not allowed to enter the craft.
"Now there will be superb viewing areas so that everyone will be able to see exactly what it is like inside."