[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.

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.

While on patrol 15 miles (24 km) east of Orford Ness on 6 July 1918, C25 was attacked by five German seaplanes returning from a raid on Lowestoft.

The commanding officer, Lieutenant David Bell and two of the lookouts on the conning tower were killed outright, the fourth man present was mortally wounded.

While the seaplanes continued their attack, the crew tried to drag him inside delaying the dive and then one of the bodies slid across the hull, their leg stopping the hatch from being closed.