The B class was an enlarged and improved version of the preceding A class. The submarines had a length of overall, a beam of and a mean draft of. They displaced on the surface and submerged. The boats could dive to a depth of. The B-class submarines had a crew of two officers and thirteen ratings. For surface running, the boats were powered by a single 16-cylinder Vickerspetrol engine that drove one propeller shaft. When submerged the propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the B class had a range of at. The boats were armed with two 18-inch torpedo tubes in the bow. 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.
Construction and career
Ordered as part of the 1904–1905 Naval Programme, B8 was built by Vickers at their Barrow-in-Furness shipyard. She was launched on 23 January 1906 and completed on 10 April at a cost of £47,000. The B-class submarines were initially assigned to the Third Division of the Home Fleet, based at Portsmouth and Devonport, and were tasked with coastal-defence duties and defending the Straits of Dover in wartime. In 1912, HMS B8, and were transferred to Malta. After the start of the First World War and the unsuccessful pursuit of the German ships Goeben and Breslau in August 1914, the B-class submarines were transferred to the Dardanelles area in mid-September to prevent any breakout attempt by the German ships. After the arrival of the larger and more modern E-class submarines in early 1915, the B-class boats began to return to Malta. After the Kingdom of Italy joined the Allies in May 1915, the B-class submarines in the Mediterranean were transferred to Venice to reinforce Italian forces in the northern Adriatic. B8, B7 and were the first to arrive in Venice on 11 October, although B8 was immediately sent to the dockyard to repair damage suffered when she collided with the Italian tugboatLuni. B8 was the first British submarine in the Adriatic to sight an enemy warship when she spotted an Austro-Hungarian destroyer off the Istrian coast on 8 November, although she was unable to attack it. The five British submarines made a total of 13 patrols off the Austro-Hungarian coast before the end of 1915, hampered by bad weather and drifting mines, followed by 13 more in the first two months of 1916. B8 reported spotting a periscope and being missed by a torpedo while beginning a patrol on 28 February; postwar research has revealed that no enemy submarines were in the area where in the incident occurred. By 27 April the boat was being refitted at Venice. After its completion in early May, the boat began her first patrol of the month on the 23rd. She was attacked by the Austro-Hungarian submarine ; the latter's torpedo missed when B8 dived upon spotting U-11s periscope. On 9 August B8 was slightly damaged when a bomb struck and sank her sister at her moorings. Replaced by more modern H-class submarines, the B-class boats returned to Malta on 9 November to be converted into surface patrol boats, armed with a 12-pounder gun. Redesignated as S8 in August 1917, the boat was assigned to patrol the Otranto Barrage that was intended to prevent the Austro-Hungarian Navy from breaking out of the Adriatic, although she proved to be very unreliable in service. Paid off at Malta, she was sold for scrap in 1919.