Lying on mudflats, this once-formidable German U-boat has been attracting attention as it lies exposed at low tide in a heap off the Kent coast.
Experts have known that the wreckage of the First World War submarine has lain on the banks of the River Medway in Hoo for nearly a century.
But the vessel - believed to be UB 122 - has been gaining more interest lately as it sits exposed, existing as a reminder of the war ahead of next year's 100th anniversary.
Mark Dunkley, maritime designation adviser for English Heritage, said it was unclear why the U-boat was not cut up and scrapped at the end of the war, like most others at the time.
He said: "Earlier this year, English Heritage commissioned research on known submarine losses in England's territorial waters.
"This research confirmed that UB 122 was surrendered to the British in November 1918 and arrived in its current position after its engines were cut out to be re-used. They were once used to power a cement factory in Halling in Kent.
"This submarine still carries with it an element of mystery as we have so far not been able to determine why the submarine was not completely cut up for scrap at the end of the war, nor salvaged for its scrap value during the Second World War.
"This was the fate of most submarines at the time."
There are no plans to conserve it, but its history will be examined in more detail after the end of the First World War commemorations.
As part of their research, marine archaeologists at English Heritage are aiming to locate dozens of British and German submarines that sank within territorial waters 12 miles off the English coast during the First World War.
Preliminary research has already identified the known sinking of 44 submarines - 41 German and three British. Local diving groups and other specialists are being enlisted to help with the project.
Some submarines could be added to the list of military maritime graves covered by the Protection of Military Remains Act 1986, which safeguards vessels from being plundered.
One protected maritime grave is the SS Mendi which lies just off the Isle of Wight.
In February 1917, 823 men, part of the South African Native Labour Corps, were en route to the Western Front when it was rammed by a British merchant ship.
More than 600 drowned, together with the crew, following the incident amid a pre-dawn fog. The wreck was identified as the Mendi in 1974.