The Supermarine Southampton was the first flying boat designed after the First World War to enter RAF service, and was the first of a series of successful military flying boats designed by Reginald Mitchell. It was based on the single Supermarine Swan flying boat, and was ordered off the drawing board in August 1924 after the Swan impressed in tests. The Southampton would become the second longest serving RAF flying boat (behind the Short Sunderland), entering service in 1925 and remaining in use for over ten years, while the related Stranraer was still in use at the start of the Second World War. The Southampton was a two-bay biplane. The lower wing was mounted just above the fuselage, and was supported by spar bracing tubes (standard practise was to build the lower wing roots into the hull). The wooden hull of the Mk I was built with an inner fuselage section with the planning bottom and two steps attached to the base. The gap between the two was divided into watertight compartments. On the metal-hulled Mk II this system was replaced by a simple single skin, which helped reduce weight and increase storage space. The two engines were mounted on pylons carried between the wings. The Southampton uses a triple fin and rudder, similar to the one used on the Swan. Three crew positions were placed ahead of the wings – the bow mooring position with a single Lewis gun was in the nose, followed by twin open tandem cockpits. The engineering and navigation stations were placed below the wing centre-section. Behind the wing were two offset Lewis gun positions.
As a replacement for the aging Rohrbach Rodra Ro.IIIas 6 were purchased in 1933 by the funds allocated from the National Budget. The planes arrived the same year and they were deployed at the newly formed company 31st Dz.Ty.Bomb.Bl. (31st Maritime Airplane Bomber Co.) located in Izmir. In 1943 they were dropped from active duty after the arrival of the Mosquitos.
The Southampton entered service in the summer of 1925 with No.480 (Coastal Reconnaissance Flight). It was best known for a series of long distance flights, carried out partly as flag waving exercises and partly to gain experience in operating flying boats in remote waters. The most famous of these tours lasted for over a year, and saw four aircraft from the Far East Flight travel 27,000 miles between October 1927 and 11 December 1928. During this journey the Southamptons circumnavigated Australia, and visited Hong Kong, Indo-China and Burma, before ending the journey at Singapore, where the flight was reformed as No.205 Squadron.