The submarine was powered by one Benz six-cylinder, four-stroke diesel engine producing 80 metric horsepower (59 kW; 79 shp), an electric motor producing 175 metric horsepower (129 kW; 173 shp), and one propeller shaft.

When submerged, she could operate for 50 nautical miles (93 km; 58 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 910 nautical miles (1,690 km; 1,050 mi) at 5 knots (9.3 km/h; 5.8 mph).

She was built by AG Weser Bremen and her complement was fourteen crew members.

One of these, the Italian Marechiaro sunk on 21 February 1916, was listed as a hospital ship and sank with over 200 casualties.

[7] Since Germany was not at war with Italy at this stage, though Austria was, UC 12, like other German U-boats in the Mediterranean, operated under the Austro-Hungarian flag.