Definition: a stream of exceptionally fast tidal flow created when the tide is forced through a constriction

The tidal races of the Pentland Firth superimposed on a Google Earth image

On coasts with large tidal ranges, the funnelling of tidal flows through a narrow strait can produce fearsome tidal currents, rips and whirlpools. At both the flood and ebb tides the sea surface can become highly agitated, with standing waves and vortices. These passages are rightly avoided by navigators, except at slack water.

The Pentland Firth is a strait with just such a reputation, with astonishing currents reported of up to 30 km/hr west of Pentland Skerries. A set of tidal races forms at different states of the tide:

The Merry Men of Mey dance off St John’s Point during the ebb tide as water pours out of the North Sea.

The Swilkie (the svelgr or Swallower in Old Norse) forms at the north end of Stroma at both ebb and flood tides. “Few having once experienced, would be rash enough to encounter a second time” The British Islands Pilot.

The Duncansby Race forms at the start of the flood but dies at the turn of the tide before reforming at the ebb. Opposing winds create horribly choppy seas.

Tidal Whirlpool Swelkie near Stroma in the Pentland Firth (AdobeStock_184931224)

The troubled surface of the Pentland Firth

The Singapore-registered tanker, which was carrying 75,000 tonnes of crude oil and is believed to have had over 20 crew on board, had loaded crude oil at Scapa Flow terminal in Orkney and was bound for Houston, Texas.

Two killed as huge waves hit oil tanker

Rob Sharp and Mike Merritt Sunday November 12, 2006
The Observer

Two crewmen were killed and another seriously injured yesterday after their oil tanker was hit by huge waves in the Pentland Firth, one of the world’s most notorious stretches of water. The men were believed to have been standing on the deck of the 42,000-tonne tanker when it was caught in a gale force eight storm and buffeted by waves over 20 feet high. The ship, the FR8 Venture, contacted Shetland coastguard shortly after midday. ‘The ship may have got hit by a freak wave.’ said the coastguard. ‘As soon as the skipper realised the extent of the injuries he turned back to Scapa Flow.’

Lifeboat – Violet, Dorothy and Kathleen – in the Pentland Firth

Share This Story, Choose Your Platform!