The C-class boats of the 1907–08 and subsequent Naval Programmes were modified to improve their speed, both above and below the surface.

[1] For surface running, the boats were powered by a single 12-cylinder[2] 600-brake-horsepower (447 kW) Vickers petrol engine that drove one propeller shaft.

On the surface, the C class had a range of 910 nautical miles (1,690 km; 1,050 mi) at 12 knots (22 km/h; 14 mph).

They could carry a pair of reload torpedoes, but generally did not as they would have to remove an equal weight of fuel in compensation.

C29 was one of the two C-class submarines sunk while attempting to employ the tactic; she was mined when her trawler Ariadne strayed into a minefield in the Humber Estuary on 29 August 1915.