Scapa Flow Scapa Flow ( or ; ) is a body of water in the Orkney Islands , Scotland , United Kingdom , sheltered by the islands of Mainland , Graemsay , Burray , South Ronaldsay and Hoy . It is about . It has a shallow sandy bottom not deeper than and most of it about deep , and is one of the great natural harbours / anchorages of the world , with sufficient space to hold a number of navies . Viking ships anchored in Scapa Flow more than 1 , 000 years ago , but it is best known as the site of the United Kingdom ' s chief naval base during World War I and World War II . The base was closed in 1956 . Viking era . The Viking expeditions to Orkney are recorded in detail in the 11th century " Orkneyinga saga s " and later texts such as the " Hákonar saga Hákonarsonar " . According to the latter , King Haakon IV of Norway anchored his fleet , including the flagship " Kroussden " that could carry nearly 300 men , on 5 August 1263 at St Margaret ' s Hope , where he witnessed an eclipse of the sun prior to sailing south to the Battle of Largs . En route back to Norway Haakon anchored some of his fleet in Scapa Flow for the winter , but he died that December whilst staying at the Bishop ' s Palace in Kirkwall . In the 15th century towards the end of Norse rule in Orkney , the islands were run by the " jarls " from large manor farms , some of which were sited at Burray , Burwick , Paplay , Hoy , and Cairston ( near Stromness ) to guard the entrances to the Flow . Wars of the Three Kingdoms . In 1650 during the wars of the Three Kingdoms , the Royalist general James Graham , 1st Marquess of Montrose , moored his ship , the " Herderinnan " , in Scapa Flow , in preparation for his attempt to raise a rebellion in Scotland which would end in failure and rout at the Battle of Carbisdale . World War I . Base for the British Grand Fleet . Historically , the main British naval bases were located near the English Channel to better face England ' s old enemies , France , Spain , and the Netherlands . In 1904 , in response to the build - up of the German Kaiserliche Marine ' s High Seas Fleet , it was decided that a northern base was needed to control the entrances to the North Sea . First Rosyth was considered for the base , then Invergordon at Cromarty Firth , but construction in both places was delayed , leaving them largely unfortified by the outbreak of WWI . Scapa Flow had been used many times for exercises in the years before the War , and when the time came for the fleet to move to a northern station , Scapa Flow was chosen for the main base of the British Grand Fleet , even though it was also unfortified . John Rushworth Jellicoe , admiral of the Grand Fleet , was perpetually nervous about the possibility of submarine or destroyer attacks on Scapa Flow , therefore starting in 1914 the base was reinforced with minefields , artillery , and concrete barriers . Only two attempts to enter the harbour were made by German U - boat s during the war , and neither was successful . tried to enter in November 1914 , but a trawler searching for submarines rammed it , causing " U - 18 " to flee and then sink . made the second attempt in October 1918 but encountered the sophisticated defences then in place . It was detected by hydrophone s before entering the anchorage , then destroyed by shore - triggered mines . After the Battle of Jutland , the German High Seas Fleet rarely ventured out of its bases at Wilhelmshaven and Kiel , and in the last two years of the war the British fleet was considered to have such a commanding superiority of the seas that some components moved south , to the first - class dockyard at Rosyth . The scuttling of the German fleet . Following the German defeat in WWI , 74 ships of the Kaiserliche Marine ' s High Seas Fleet were interned in Gutter Sound at Scapa Flow pending a decision on their future in the peace Treaty of Versailles . On 21 June 1919 , after nine months of waiting , Rear Admiral Ludwig von Reuter , the German officer in command at Scapa Flow , made the decision to scuttle the fleet because the negotiation period for the treaty had lapsed with no word of a settlement ( he was not kept informed that there had been a last - minute extension to finalise the details ) . After waiting for the bulk of the British fleet to leave on exercises , he gave the order to scuttle the ships to prevent their falling into British hands . The Royal Navy made desperate efforts to board the ships to prevent the sinkings , but the German crews had spent the idle months preparing for the order , welding bulkhead doors open , laying charges in vulnerable parts of the ships , and quietly dropping important keys and tools overboard so valves could not be shut . The British did eventually manage to beach the battleship , the light cruisers " Nürnberg " , " Frankfurt " and " Emden " , together with 18 destroyers , but the remaining 52 ships , the vast bulk of the High Seas Fleet , were sunk without loss of life . Nine German sailors died when British forces opened fire as they attempted to scuttle their ship , reputedly the last casualties of WWI . The great salvage operation . Although many of the larger ships turned turtle and came to rest upside down or on their sides in relatively deep water ( 25 – 45 m ) , some — including the battlecruiser — were left with parts of their superstructure or upturned bows still protruding from the water or just below the surface . They posed a severe hazard to navigation , and small boats moving around the Flow regularly became snagged on them . The Admiralty initially declared that there would be no attempt at salvage , that the sunken hulks would remain where they were ; in the first few years after the war , there was abundant scrap metal as a result of the huge quantities of leftover tanks , artillery and ordnance . By the early twenties , the situation had changed . In 1922 , the Admiralty invited tenders from interested parties for the salvage of the sunken ships , although at the time few believed that it would be possible to raise the deeper wrecks . The contract went to a wealthy scrap metal merchant , Ernest Cox , who created a new company , Cox & Danks Ltd , for the venture , and so began what is often called the greatest maritime salvage operation of all time . During the next eight years , Cox and his workforce of divers , engineers , and labourers engaged in the complex task of sealing the multiple holes in the wrecks and welding huge steel tubes to the hulls to allow compressed air to be pumped into the ships to raise them . First the relatively small destroyers were brought to the surface and sold for scrap to help finance the operation , then the bigger battleships and battlecruisers . Cox endured bad luck and frequent fierce storms which often ruined his work , swamping and re - sinking ships which had just been raised . At one stage , during the General Strike of 1926 , the salvage operation was about to grind to a halt due to a lack of coal to feed the boilers for the water pumps . Cox ordered that the abundant fuel bunkers of the sunken battlecruiser be broken into to extract the coal with mechanical grabs , allowing work to continue . Although he ultimately lost money on the contract , Cox kept going , employing new technology and methods as conditions dictated . By 1939 , Cox and the company he later sold out to , Metal Industries Ltd , successfully raised 45 of the 52 scuttled ships . The last , the massive , was raised from a record depth of 45 metres just before work was suspended with the start of WWII , before being towed to Rosyth where it was broken up in 1946 . A Morse key recovered from the battleship during the salvage operation is now on display at the Museum of Communication , 131 High Street , Burntisland , Fife , Scotland . World War II . Primarily because of its great distance from German airfields , Scapa Flow was again selected as the main British naval base during WWII . The strong defences built during WWI had fallen into disrepair , however : defence against air attack was inadequate , while blockships sunk to stop U - boats from penetrating had largely collapsed . While there were anti - submarine nets in place over the three main entrances , they comprised only single - stranded looped wire . There was also a severe lack of the patrolling destroyers and other anti - submarine craft that had previously been available ; efforts began belatedly to repair peacetime neglect but were not completed in time to prevent a successful penetration by enemy forces . On 14 October 1939 , under the command of Günther Prien , penetrated Scapa Flow and sank the WWI – era battleship anchored in Scapa Bay . After firing its first torpedo , the submarine turned to make its escape ; but , upon realising that there was no immediate threat from surface vessels , it returned for another attack . The second torpedo blew a 30 - foot ( 9 m ) hole in the " Royal Oak " , which flooded and quickly capsized . Of the 1 , 400 - man crew , 833 were lost . The wreck is now a protected war grave . Three days after this submarine attack , four Luftwaffe Junkers Ju 88 bombers raided Scapa Flow in one of the first bombing attacks on Britain during the war . The attack badly damaged an old base ship , the battleship , with one bomber shot down by an anti - aircraft battery on Hoy . New blockships were sunk , booms and mines were placed over the main entrances , coast defence and anti - aircraft batteries were installed at crucial points , and Winston Churchill ordered the construction of a series of causeways to block the eastern approaches to Scapa Flow ; they were built by Italian prisoners of war held in Orkney . These " Churchill Barriers " now provide road access from the mainland to Burray and South Ronaldsay , but block maritime traffic . An air base , RAF Grimsetter ( which later became ) , was built and commissioned in 1940 . Today . Use by the petroleum industry . Scapa Flow is one of the transfer and processing points for North Sea oil . A 30 - inch , 128 - mile - long underwater pipeline brings oil from the Piper oilfield to the Flotta oil terminal . The Claymore and Tartan oil fields also feed into this line . Scapa Flow Visitor Centre . The Scapa Flow Visitor Centre , at Lyness on the island of Hoy , is located in the former naval fuel pumping station and a converted storage tank . Exhibits include a large , three - dimensional representation of the island and of the German ships as they were prior to scuttling . The island is accessible by local ferry several times daily from Houton . The centre has catering facilities for day trippers . Scuba diving . The wreckage of the remaining seven ships of the German fleet ( and some other sites such as the blockships ) has become increasingly popular as a venue for recreational scuba divers , and is regularly listed in dive magazines and internet forums among the top dive sites in the UK , Europe , and even the world . Although other locations , for example the Pacific regions , offer warmer water and better visibility , there are very few other sites which can offer such an abundance of large , historic wrecks lying in close proximity and shallow , relatively benign diving conditions . As of 2010 , at least twelve " live aboard " boats — mostly converted trawlers with bunk rooms in their former holds — take recreational divers out to the main sites , primarily from the main harbour at Stromness . Diving provides a substantial amount of trade and income for the local economy . Divers must first obtain a permit from the Island Harbour Authorities , which is available through diving shops and centres . The wrecks are mostly located at depths of 35 to 50 metres . Divers are permitted to enter the wrecks , but not to retrieve artefacts located within 100 metres of any wreck . However , time and tide has washed broken pieces of ships ' pottery and glass bottles into shallow waters and onto beaches . The underwater visibility , which can vary between 2 and 20 metres , is not sufficient to view all the length of most wrecks at once ; however , current technology is now allowing 3D images of them to be seen . The important wrecks are : The battleships . The three sister battleships of the , the , and , which together formed the main component of the 3rd Battleship Squadron , and which took part in some of the fiercest fighting at Jutland , lie upside down with around 25m of water over them . Although they were never raised , they have been substantially salvaged over the years , with armour plate blasted away and non - ferrous metals removed . They remain , however , extremely impressive dives , not least because of their sheer , awesome size . The light cruisers . Having much less bulky fighting tops , the four light cruiser s , , , and lie on their sides with around 16 – 20 metres of water over them . With the exception of the shallower " Karlsruhe " , they have been less heavily salvaged than the battleships and are much more accessible for divers . Other dive locations . Additional sites of interest include the destroyer , which was raised and used by Cox as a working boat during his salvage operations , particularly on the , then later abandoned ; the Churchill blockships , such as the " Tabarka " , the " Gobernador Bories " , and the " Doyle " in Burra Sound ; the U - boat ; and the trawler " James Barrie " . Also , some large items from many of the ship hulls that " were " raised ( such as the main gun turrets , which fell away from the ships as they capsized ) were never salvaged , and still exist on the seabed in close proximity to the impact craters created by the scuttled ships . The forbidden wrecks . The wrecks of and the dreadnought , which exploded at anchor during WWI , are war grave s protected under the Protection of Military Remains Act 1986 . In addition , the wreck of the , which hit a mine while carrying Lord Kitchener north to Murmansk on 5 June 1916 and sank off the west coast of the mainland , is also a protected site . The 10 , 850 - ton armoured cruiser , which went down in a heavy storm four days after the Battle of Jutland with only 12 surviving from its 655 crew , lies in 70 metres of water 1 . 5 miles off the steep , desolate cliffs of Marwick Head , above which the Kitchener Memorial now stands as a memorial to those lost . Only divers of the British armed forces are permitted to visit them .