The "Butt of Lewis" Lewis Point, Outer Hebrides, Scotland at the top of the map. The "Butt"/Point is the closest point where a suspected encounter with a Russian submarine occurred. On the right is the UK (Scottish) mainland.
Faslane Naval Base is in Gare Loch. A Russian submarine may regularly stay on station around 50km or more out to sea.
Several UK media outlets have carried a mid-March 2015 report that a submarine snagged on a large net almost dragged a UK (Scottish) trawler under. The reported encounter occurred near the "Butt of Lewis" Lewis Point, Outer Hebrides, Scotland.
If it was a Russian submarine it was probably a Russian attack submarine (Kilo SSK or Akula SSN) submarine from the Russian Northern or Baltic Fleets. Russian SSBNs would steer clear of northern Scotland where the encounter occurred.
One of the Russian Kilos or Akulas submarines was probably travelling to or from its regular surveillance area where UK (and perhaps US) submarines enter and leave the Faslane Naval Base (HMNB Clyde) 40 km northwest of Glasgow, Scotland. The Russian submarines would ideally wish to follow UK/US submarines leaving Faslane and also intercept UK telecommunications.
Submarine-Trawler Incidents Have a Long History
The revelation of a possible Russian submarine encounter follows more than 100 years of submarines accidentally damaging or wrecking trawlers through net snags and also collisions.
In 2005 the Guardian reported: "Large submarines have also been caught in fishing nets, but usually, the trawlers come off worse. In 1990, four fishermen died when their trawler was dragged under by a British submarine on a training exercise off the west coast of Scotland. A few weeks later, an American submarine ploughed into the nets of a trawler from Northern Ireland, making the vessel heave before ripping the net from its winches."
Submarine collisions destroying small ships also occur. In February 2001, while conducting an emergency main ballast tank blow off the coast of Oahu USS Greeneville struck and sank the 191-foot (58 m) Japanese fishery high school training ship Ehime Maru.