The company designation, 2F.1, meant that the Nautilus was Blackburn's first two-seat fighter, though it was really intended as a carrier-based fleet spotter with interception capability.

All these were powered by the V-12 water-cooled Rolls-Royce F.XIIMS - later known as the Kestrel IIMS - which produced 525 hp (391 kW) and had a small cross-sectional area.

[1] The slim power unit encouraged the design of slender, well-streamlined fuselages, and the nose of the Nautilus was longer and more pointed than even that of the Ripon III, which used a larger area W-12 Napier Lion engine.

Like most of Blackburn's aircraft of the time, the fuselage was built up around four steel longerons; it was duralumin-covered from the nose to just aft of the rear observer/gunner's cockpit, the rest fabric-covered.

Both the tailplane incidence and (more unusually) the alignment of the upper part of the fin could be adjusted in flight via trimming wheels.

As a seaplane, it could be fitted either with a two-float arrangement or with a single central float, the latter intended to give a better field of view to the observer.