[1] For surface running, the boats were powered by a single 16-cylinder 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.

On 17 April 1915, the submarine HMS E15 attempted to break through the Dardanelles in order to attack shipping in the Sea of Marmara.

[6][7] E15 was finally torpedoed and sunk by picket boats from the Battleships Majestic and Triumph on the night of 18 April.

The two submarines had orders to patrol off Sollum, but were found to be unsuited to this duty, being too small and having too short a range and so were withdrawn from the operation.