The Dewoitine HD.730 was developed as a two-seat shipborne observation and artillery-spotting seaplane for the French Navy (Marine Nationale). Designed to replace the older Loire 130 biplanes, the aircraft was intended to be launched from shipboard catapults and recovered via crane. The project was a Dewoitine design managed under the nationalized company SNCAM (Société Nationale de Constructions Aéronautiques du Midi). On March 19, 1938, the French Navy ordered two prototypes from SNCAM's Toulouse plant, though subsequent industrial restructuring saw the aircraft transferred to SNCASE (Société Nationale de Constructions Aéronautiques du Sud-Est) for completion and testing.
Technically, the HD.730 was a departure from previous naval designs, featuring an all-metal, low-wing monoplane configuration with twin main floats. To reduce drag while maintaining hydrodynamic stability, the aircraft utilized retractable wing-tip stabilizing floats. The crew of two—a pilot and an observer/gunner—were housed in enclosed cockpits to improve aerodynamics and comfort. The aircraft was powered by a single Hispano-Suiza 12Xcrs inverted V-12 liquid-cooled piston engine, producing between 690 and 720 hp. Performance figures indicate a maximum speed of approximately 280–300 km/h, a cruise speed of 240–250 km/h, and a service ceiling of roughly 7,000 meters, with a range of 1,000–1,100 km. Its dimensions included a wingspan of 13.0–13.3 meters and a length of 10.4–10.8 meters.
Flight testing began at Lac de Berre near Marignane, with the first prototype (HD.730.01) flying in February 1940, followed by the second prototype (HD.730.02) in May 1940. Despite the modern design, test reports indicated the aircraft was underpowered. This led to proposals for a more powerful engine and a reduction in the planned order of 40 aircraft. The program was disrupted by the Battle of France in June 1940. Under the Vichy government, a third, heavily modified airframe designated the HD.731 flew in March 1941 as a liaison aircraft, utilizing a different, more powerful engine. However, no series production ever followed, and the project became a technical dead end. No examples of the HD.730 or HD.731 are known to have survived.