The Pentland Firth, which is actually more of a strait than a firth, separates the Orkney Islands from Caithness, which is in the far north of the Highland area of Scotland. On its Caithness (southern) side the Firth extends from Dunnet Head to Duncansby Head. Simplified diagram A strait is a narrow channel of water that connects two larger bodies of water, and thus lies between two land masses. ... Firth is the Scots word often used to denote a large sea bay in Scotland, which may be part of an estuary, or just an inlet, or even a strait (as in the case of the Pentland Firth). ... The Orkney Islands form one of 32 unitary council regions in Scotland, and are a Lieutenancy Area. ... Caithness (Gallaibh in Gaelic) is a traditional county and former administrative county which is now within the Highland area of Scotland. ... Highland (a Ghaidhealtachd in Gaelic) is the name of the largest administrative region in Scotland. ... Scotland (Scottish Gaelic: Alba) is a country in northwest Europe, occupying the northern third of the island of Great Britain. ... Contrary to popular opinion, the most northerly point on the island of Great Britain is not John OGroats, but 20 kilometres west at the northern tip of Dunnet Head. ... Duncansby Head point ( 58°3843N and 03°0123W Grid reference: ND405735) is the point on mainland Great Britain where Pentland Firth water meets the more open water of the North Sea. ...

In the middle of the Firth are two significant islands, Stroma and Swona. The small Pentland Skerries group are in the east. The islands of Hoy and South Ronaldsay border the firth to the north and are part of the Orkney Islands. The island of Stroma, which in the Norse means ‘Island in the Stream’, is the southern of the two islands situated in the Pentland Firth between the Orkney Islands and Caithness on the Scottish mainland. ... The island of Swona (Norse for “Swains Island”) is the northern of the two islands situated in the Pentland Firth between the Orkney Islands and Caithness on the Scottish mainland. ... The Pentland Skerries are a group of four uninhabited islands lying in the Pentland Firth, north east of Duncansby Head and south of South Ronaldsay in Scotland. ... Hoy shown within Orkney Islands Hoy (from Old Norse há-øy meaning high island) is one of the Orkney Islands. ... South Ronaldsay shown within Orkney Islands South Ronaldsay is one of the Orkney Islands in Scotland. ... The Orkney Islands form one of 32 unitary council regions in Scotland, and are a Lieutenancy Area. ...

The most northly point of the headland of Dunnet Head , Easter Head, is also that of mainland Britain. The famous John o' Groats, Mey (site of the Castle of Mey), and many smaller villages are also to be found on the Caithness side. The bay at San Sebastián, Spain A Headland is an area of land adjacent to water on three sides. ... Location within the British Isles. ... The Castle of Mey (formerly Barrogill Castle) is in dramatic situation on the north coast of Scotland, about 6 miles west of John OGroats. ...

The town of Thurso and Scrabster Harbour are on the Caithness shore on the western fringe of the Firth. A ferry runs through this fringe from Scrabster to Stromness on the Orkney Mainland. Across the Firth itself a ferry runs from Gills Bay near John o' Groats to St Margaret's Hope on South Ronaldsay and, in the summer months, a passenger-only ferry runs from John o'Groats to Burwick on South Ronaldsay. St. ... Stromness is the second-largest town in the Orkney Islands and is located on the southwestern edge of the mainland of Orkney. ... The Mainland, Orkney shown within The Orkney Islands The Mainland is the main island of Orkney, Scotland. ... St Margarets Hope is the third largest town in Orkney after Kirkwall and Stromness with a population of around 550. ... South Ronaldsay shown within Orkney Islands South Ronaldsay is one of the Orkney Islands in Scotland. ...

The Firth is well known for the strength of its tides, being among some of the fastest in the world, a speed of 16 knots being reported close west of Pentland Skerries. The force of the tides give rise to overfalls and tidal races which can occur at different stages of the tide. Some of the principal tidal races are;- A knot is a non SI unit of speed equal to one nautical mile per hour. ...

‘The Merry Men of May’. Forms off St Johns point in the west going stream and extends as the tide increases NNW across the firth to Tor Ness. The worst part is over a sand wave field about 3 ½ miles west of Stroma. The waves formed by this race form a natural breakwater with relatively calm water to the east of it, particularly noticeable when a westerly swell is running. Tides in this area can exceed 10 kts.

‘The Swilkie’. The race at the north end of Stroma, off Swilkie Point is known as ‘The Swilkie’. It extends from the point in an easterly or westerly direction depending on the tide and can be particularly violent. The whirlpool of the same name was, according to a Viking legend, caused by a sea-witch turning the mill wheels which ground the salt to keep the seas salty. This article is about stroma in biology. ...

The ‘Duncansby Race’ forms off Ness of Duncansby at the start of the SE going tidal stream (flood). Initially extending ENE but wheeling gradually anti-clockwise until it extends about 1 ml. NW some 2 ½ hrs later at which point it is known as ‘The Boars of Duncansby’. During the time of the SE stream there is additional turbulence off Duncansby Head, particularly to the East. The race temporarily ceases at the turn of the tide before forming in an ENE direction in the NW going tidal stream (Ebb) before ceasing again at the next turn of the tide. The race is particularly violent and dangerous when the tidal stream is opposed by gales in the opposite direction. During the east going stream a race forms off Ness of Huna. This race can be particularly violent in an easterly or south easterly gale.

The ‘Liddel Eddy’ forms between South Ronaldsay and Muckle Skerry in the East going stream (flood). A race also forms for part of the time off Old Head at the SE part of South Ronaldsay.

In addition to ‘The Swilkie’, races form at both the north and south ends of Stroma and Swona. Between the races there is a calm eddy which extends down tide as the tide strengthens. The races are highly visible with over falls and whirlpools. Large swell waves can also be present, especially in bad weather conditions. When entering or leaving the eddies, crossing the races, even large powerful vessels can be pushed off course, such is the demarcation between the relatively calm eddy and the fast moving tide in the races. There are other races in the firth particularly off Brough Head.