The ghost of U-Boat 33: German sub sunk in 1918 threatening to surface in Channel

De Duitse onderzeeër UB-33, die in de Eerste Wereldoorlog vanuit Zeebrugge opereerde en in de Straat van Dover op een mijn liep, dreigt weer boven water te komen in de drukke vaarroute die door Kanaalferries wordt gebruikt.

It was one of the deadliest submarines in the German Navy's fleet out of Zeebrugge during the First World War. The UB-33 stalked the seas - sinking at least 13 craft as it marauded across the English Channel and North Sea in search of Allied vessels. Finally, the hunter met its own end eight miles off Dover in 1918. But now, 89 years on, the ghost of the submarine is threatening to rise from the depths - to pose a new danger to cargo ships, tankers and ferries in the Channel, the world's busiest shipping lane. Lying in shallow waters, the wreck of the UB-33 has been disturbed by passing vessels, leading to fears that it could break free from the seabed and rise to the surface. So a salvage operation has been launched to prevent it hitting any of the hundreds of ships that cross the Channel each day. The saga began when UB (Unterseeboot) 33 was sunk with all 28 crew on April 11, 1918, after hitting a mine around the Varne Bank sandbank in the Dover Strait. It was armed with six torpedoes, two already loaded in its forward tubes. The area is directly beneath the shipping lane now used by ferries travelling to Calais and Boulogne and much of the movement of the wreck has been caused by the turbulence of vessels travelling above it. Currently, the UB-33 is lying 77ft down, but the official minimum clearance depth is 87ft. Trinity House - the institution which marks shipping lanes and maintains lighthouses - has temporarily stationed a vessel over the spot to warn ships. It was orginally thought the wreck could simply be blown up. However, that cannot be done because of the vessel's status as a registered war grave. Another option would be to mark its position with a large buoy. But the Varne Bank area is so busy that one shipping source said this would be like "putting a speed hump in the fast lane of the M4". A Trinity House spokesman said there are now alternative plans to gently move the UB-33 to deeper water. "It has been there a long time, but now the wreck has started to move and it is causing concern as it has once again become a danger to shipping," explained Vikki Gilson. "We have had divers surveying the wreck and one solution would be to re-set the wreck in a deeper position. It has been a hazardous job for the divers, but their survey is now complete. In the next few weeks, when conditions are right, we are hopeful we can move the boat." Trinity House says it is not officially confirming the identity of the U-boat out of respect for the families of the dead crew. "It is a sensitive situation because it is a war grave and we would not like to get anything wrong." The 324-ton UB-33, officially designated a coastal torpedo attack boat, sank three years after being launched. It was capable of doing 45 miles at 5 knots (5.8mph) submerged and involved in a total of 17 patrols. During that time, it destroyed 13 ships, damaged two others and took three as prizes. The submarine, commanded by First Lieutenant Fritz Gregor, slipped its moorings for the last time when it sailed out of the Belgian port of Zeebrugge - then in the hands of the Germans - on the night of April 10, 1918. It hit the mine the following day. It was one of more than 1,000 such boats which sank hundreds of thousands of tons of Allied shipping during the First World War. But 182 U-boats were sunk between 1914 and 1918 - and today the wrecks of some 133 lie around the coast of Britain. During the Second World War, a further 666 U-Boats were sunk and many of them are still legally protected as war graves.