Scapa Flow (/ˈskɑːpə/ or /ˈskæpə/; from Old Norse Skalpaflói 'bay of the long isthmus' 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 has a shallow sandy bottom not deeper than 60 metres (200 ft) and most of it about 30 metres (98 ft) deep, and is one of the great natural harbours/anchorages of the world, with sufficient space to hold a number of navies. Scapa Flow is one of Britain's most historic stretches of water - located within the Orkney Islands, off the northeast coast of Scotland. Its sheltered waters have been used by ships since prehistory and it has played an important role in travel, trade and conflict throughout the centuries - especially during both World Wars. It is currently a world-famous diving location, with the wrecks of the scuttled German Fleet offering unique diving challenges. Scapa Flow is also a major oil port serving the Flotta Oil Terminal, and is a prime location of ship-to-ship transfers of crude oil product and liquefied natural gas (LNG). The world’s first ship-to-ship transfer of LNG took place in Scapa Flow in 2007.
The Viking expeditions to Orkney are recorded in detail in the 11th century Orkneyinga sagas 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, at St Margaret's Hope on 5 August 1263 where he witnessed an eclipse of the sun prior to sailing south to the Battle of Largs. On 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.