Commissioned in , she served during World War I and was stricken in They had an overall length of Their crew numbered two officers and 23 enlisted men. For surface running, the submarines were powered by two metric-horsepower bhp ; kW triple-expansion steam engines , each driving one propeller shaft using steam provided by two Du Temple boilers. When submerged, each propeller was driven by a metric-horsepower bhp; kW electric motor.
The first six submarines completed were armed with a single millimeter All of the submarines were fitted with six millimeter Following a ministerial order on 22 February , the aft tubes were reversed so they too fired forward, but at an angle of eight degrees.
The other launchers were a rotating pair of Drzewiecki drop collars in a single mount positioned on top of the hull at the stern. They could traverse degrees to each side of the submarine. Watt , named after the British 18th-century inventor James Watt , was ordered on either 26 August [ 6 ] or 19 October [ 7 ] according to different sources from the Arsenal de Rochefort in Rochefort , France.
During her builder's sea trials , she suffered steam engine damage on 21 December that forced her to interrupt her trials and return to port. Watt was completed in Watt struck either a breakwater , jetty , mole , or seawall as she returned to her anchorage on 3 December She suffered bow damage with an estimated repair time of two months.
By , Watt was based at Brest , France. After the declaration of war, Watt conducted patrols in the English Channel , and from September to June she was based in England at Portsmouth as part of defense agreements between France and the United Kingdom. She patrolled off Algeria and in the Strait of Sicily.
