Otraria was one of two Argo-class submarines ordered by the Portuguese government, but taken over and completed for the Regia Marina (Royal Italian Navy) during the 1930s.

The Glauco-class submarines were improved versions of the preceding Squalo class.

[1] For surface running, the boats were powered by two 1,500-brake-horsepower (1,119 kW) diesel engines, each driving one propeller shaft.

On the surface, the Glauco class had a range of 9,760 nautical miles (18,080 km; 11,230 mi) at 8 knots (15 km/h; 9.2 mph); submerged, they had a range of 110 nmi (200 km; 130 mi) at 3 knots (5.6 km/h; 3.5 mph).

They were also armed with two 100-millimeter (3.9 in) deck guns, one each fore and aft of the conning tower, for combat on the surface.