[1] For surface running, the boats were powered by two 800-brake-horsepower (597 kW) Vickers two-stroke diesel engines, each driving one propeller shaft.

On the surface, the G class had a range of 2,400 nautical miles (4,400 km; 2,800 mi) at 16 knots (30 km/h; 18 mph).

[1] Like the rest of her class, G11's role was to patrol an area of the North Sea in search of German U-boats.

Sailing through dense fog, she overshot Blyth and ran aground on rocks below cliffs near Howick, some 30 mi (48 km) to the north.

[2][3] G11's regular captain Lieutenant Richard Douglas Sandford VC had not sailed on her last mission, having succumbed to typhoid fever.