The name is presumed to be a corruption of the Old Norse "Petlandsfjörð",[1] meaning "the fjord of Pictland", and is completely unrelated to the Pentland Hills near Edinburgh.

Such was their marine prowess that there are also instances of this name referring to the sea lanes of the entire west coast of Scotland down to Kintyre.

One version of the 9th-century Historia Brittonum states that "the Britons originally filled the whole island with their peoples from the English Channel to the Sea of Orcs".

The Far North Line opened 28 July 1874 Historically the Gills Bay area has been the main setting off point from the mainland to the islands of Stroma and Swona and Orkney itself.

At present Pentland Ferries operate on this route from Gills Bay to St Margaret's Hope on South Ronaldsay.

The 10-mile (16 km) tunnel was initially projected to have cost £100 million based on preliminary studies carried out in 2005 but as of 2012 no further progress has been made.

It has since been swum by others including Andrea Gellan (2011; fastest swim) Mark Cameron (2018) and Alison Lievesley (2020) The Firth is well known for the strength of its tidal currents, which are among the fastest in the world, a speed of 30 kilometres per hour (16 kn) being reported close west of Pentland Skerries.

Combined with gale-force winds, they often give rise to extremely violent sea conditions, which have caused accidents such as the 2015 sinking of the cargo ship MV Cemfjord that resulted in the death of eight crew members.

[citation needed] Currents of up to 5 metres per second (11 mph) make the Pentland Firth potentially one of the best sites in the world for tidal power.

The SNP Energy Review of July 2006 claimed that the Firth could produce "10 to 20 GW of synchronous electricity"[13] and First Minister Alex Salmond claimed that the Pentland Firth could be "the Saudi Arabia of tidal power"[14] with an output of "20 gigawatts and more than that".

[14][15] In July 2013 Thomas Adcock of Oxford University stated that the Firth "is almost certainly the best site for tidal stream power in the world"[16] although a peer-reviewed study he led suggested that the maximum potential of the Firth was 1.9 GW of tidal power, with one GW being a more realistic figure.

[17] In October 2010 MeyGen, a consortium of ARC, Morgan Stanley and International Power, received operational lease from the Crown Estate to a 400 MW project for 25 years.

[20] MeyGen completed the longest-ever run of continuous tidal electricity generation in 2019 with 25 GWh produced, enough to power nearly 4,000 homes.

Grows to 7–8.5 m, black with diagonal white band on flipper and a slender, pointed triangular head.

Will probably see the long back with small fin to rear breaking the surface although they are known to bow and stern ride the waves of vessels.

Usually seen feeding inshore at high tide around here in the Gills Bay, Stroma, area though may be seen in deeper water.

There are four other species less frequently encountered in UK waters where they usually occur as stray juveniles carried by currents from warmer seas.