The wreck of a World War One German U-boat has been found off the coast of Norfolk.
Scans by windfarm developers showed the submarine lying about 55 miles (90km) east of Caister-on-Sea.
U-31 went missing in January 1915, struck a mine in the North Sea and sank. All 35 men on board died. Its whereabouts were not known until now.
As an official military maritime grave, the wreck of U-31 will remain in its final resting place.
U-31 was the first of 11 Type U-31 submarines to be commissioned by the Imperial German Navy between 1912 and 1915.
Numbered from 31 to 41, three surrendered and eight sank. The whereabouts of two of those that sank - including U-31 - was unknown, Mark Dunkley, marine archaeologist at Historic England, said.
He called the discovery by windfarm developers ScottishPower Renewables and Vattenfall "a significant achievement".
Scans of the seabed turned up more than 60 wrecks over a two-year period. Most of these were already known about, but the U-boat was "entirely unexpected", developers said.
At first it was thought the wreckage might be a Dutch Navy submarine, missing since June 1940, however, after several dives it was eventually found to be the much earlier German submarine.
A team from Lamlash North Sea Diving managed to get clear footage of the U-boat, lying on the seabed at a depth of 98ft (30m), allowing accurate identification of U-31.
U-boats and U-31
- U-31 was one of 375 German submarines - U-boats - that set sail from German ports in World War One
- They had a range of about 8,000 nautical miles (14,800km)
- Sailors could spend around five days on war patrol but only had 72 hours' air supply
- 202 U-boats were lost in action during the war
- Out of 17,000 men who served on board them, more than 5,100 lost their lives.
- U-31 left Wilhelmshaven in Germany on a routine patrol and disappeared on 13 January 1915
- It is believed it hit a mine and sank. All four officers and 31 men were lost
- U-31 is 190ft (57.6m) in length, 13ft 6in (4.1m) wide and 19ft 6in (4.6m) high
- Its bow had been damaged and debris surrounding it suggested U-31 could have been up to 230ft (70m) long
Source: BBC iWonder/ScottishPower Renewables
"After being on the seabed for over a century, the submarine appears to be in a remarkable condition with the conning tower present and the bows partially buried," Mr Dunkley said.
"Relatives and descendants of those lost in the U-31 may now take some comfort in knowing the final resting place of the crew and the discovery serves as a poignant reminder of all those lost at sea, on land and in the air during the First World War."
Should plans for a windfarm in the area go ahead, developers have given assurances the site will not be disturbed.