It was designed by Supermarine to meet a 1917 Navy Board specification which stipulated the aircraft have a speed of 95 knots (176 km/h; 109 mph), a ceiling of 20,000 feet (6,100 m), and be capable of being launched from ships at sea.

One of the designs for the Baby formed the basis for other aircraft, including the Supermarine Sea Lion I which participated in the 1919 Schneider Trophy race.

The Baby was designed and built under the direction of the owner of Supermarine, Hubert Scott-Paine, who had joined Pemberton-Billing Limited in 1911.

Scott-Paine bought out its original owner, Noel Pemberton Billing, in June 1916, after which the company was renamed Supermarine Aviation Works Limited.

During the First World War, the company continued to specialise in producing and maintaining marine aircraft, as testified by its location at Woolston on the banks of the River Itchen, its lack of an aerodrome and its maintenance of a workforce skilled in constructing boats.

[1] The Baby was notable for being the first single-seat flying boat fighter aircraft to be designed and built in the United Kingdom.

[2][note 1] The specification was for a single seat floatplane or flying boat fighter to counter the German Brandenburg aircraft patrolling the North Sea.

[2] On awarding the contract, the AD established its presence at Supermarine by sending one of its lead designers, Harold Bolas, and his deputies to oversee the production of the Baby.

[3][note 2] Hargreaves based his design on the AD Flying Boat, [3] a two-seater sea patrol and reconnaissance biplane with a poor performance record that had a flexible, tubular body and wings separated by four vertical struts that folded forwards.

[9][10] Hargreaves produced a design for a pusher biplane with a small single engine, folding single-bay wings and a T-tail.