The Short S.81 was an experimental British gun-carrying pusher biplane seaplane ordered from Short Brothers by the British Admiralty in 1913 for use by the Royal Naval Air Service.The seaplane, manufacturers serial number S.81, was built at Eastchurch and allocated the military serial number 126. S.81 was delivered to Calshot on 25 May 1914 and accepted by the Navy on 2 June 1914. It had three-bay wings with overhanging upper wings, and was powered by a 160 hp (119 kW) Gnome rotary engine.