U-18 was a steel U-17 class submarine launched from Kaiserliche Werft, Danzig yard on 25th April 1912. Submarine in this class measured 198.25′ x 20.0′ x 11.2′ and displaced 564 tons on the surface and 691 tons when submerged. They carried only 6 torpedoes fired from their 2 stern and two bow torpedo tubes and had a single 105 mm deck gun.
In the early days of World War One unconfirmed sightings of enemy U-boats around the north of Scotland caused great anxiety at the Admiralty. Scapa Flow was the most important anchorage for the British High Seas fleet and its war defences were still unfinished. On the 22nd November the decision was made to move the fleet to ports on the east coast of Scotland until the work was complete. This followed an incident 1st September when a lookout on a ship in Scapa Flow raised the alarm, believing he had seen a periscope in the harbour. The fleet put to sea in a great hurry, some ships even firing their guns at what they thought were periscopes. In fact no U-boats had entered the anchorage. The episode became known as the First Battle of Scapa Flow. There was a repeat performance just six weeks later, and so, in November, Jellicoe ordered his fleet dispersed until the defences were in place.
Meanwhile, on 14th November 1914 U-18 set off from her base in Heligoland on her third patrol of the war heading for Orkney under the command of Kapitanleutnant Heinrich Von Henning with a crew of 26 men aboard. By night time on the 22nd they had reached a position south east of the Orkneys and, sighting searchlights in the direction of Scapa Flow and thinking the fleet there, Von Henning decided to make an audacious attack on the anchorage itself. As U-18 approached the Pentland Firth he was surprised to see the Pentland Skerries lighthouse lit. He could not know this was to aid the fleet’s evacuation from Scapa earlier that night.
Around 11am on the 23rd U-18 dived and entered Hoxa Sound secretly following a steamship through the open boom defence nets but, as they rose to periscope depth, Von Henning could see that the anchorage was empty. He turned to make his way back out through the Hoxa boom and return to the open sea but at this point their luck ran out. U-18’s periscope was spotted by seamen aboard the examination steamer Tokio, who raised the alarm, and within a few minutes dozens of small support vessels that remained in the Flow after the fleet departed were searching for the submarine.
At 12.10pm minesweeper No 96, which in peacetime was the Aberdeen steam trawler Dorothy Gray, was patrolling the entrance to Hoxa Sound. Her skipper, Captain. Youngson RNR, spotted the submarines periscope 1.25 miles off Hoxa Head. An instant decision was made and the trawler raced full speed ahead directly towards the periscope and rammed the U-boat. The Dorothy Gray lifted three feet in the air and the U-boat was thrown on its beam ends with her steering gear and hydroplanes damaged and periscope bent over at right angles. Von Henning seemed in a hopeless position with a blind, half-crippled submarine but again the U-18 dived still trying to make the open sea. In fact, he did manage to reach the open sea but, unable to maintain depth due to the damaged hydroplanes, U-18 struck the seabed so hard that it sent her once more to the surface. Almost immediately she was rammed again, this time by the destroyer HMS Garry. U-18 made one last effort to escape diving again, this time hitting the seabed at 230 feet damaging her propellers and starting a fire in the battery room.
Von Henning had no choice but to surrender. All tanks were blown and the U-18 surfaced. The crew quickly scrambled on deck, raised a white flag and fired star shells into the air. Two destroyers, HMS Erne and HMS Garry sped towards the U-boat. However Von Henning had already given the order to open the seacocks and scuttle his submarine. As HMS Garry came alongside U-18 sank and the crew jumped clear into the water. Three officers and 23 of the crew then swam to the destroyer and were taken prisoner but one crewman drowned.
The wreck of the U-18 lies in position 59° 42.129′ N, 002° 48.080′ W (WGS84) in 70 metres of water oriented 163/343 degrees with bows facing north west. The submarine is reported to be sitting upright on an undulating sandy seabed and is fairly well preserved for a vessel lost in World War One. The bow plates have rotted through but the collision damage is still visible near the stern and the bent hydroplanes are also apparent. The open hatch where the crew scrambled free is also visible on the stern deck.