Italian submarine Smeraldo

Smeraldo was one of a dozen Sirena-class submarines, the second sub-class of the 600 Series of coastal submarines built for the Regia Marina (Royal Italian Navy) during the early 1930s.

Design and description
The Sirena class was an improved and enlarged version of the preceding Argonauta-class submarines. They displaced 680 LT surfaced and 837 LT submerged. The submarines were 61.5 m long, had a beam of 5.7 m and a draft of 4.7 m. Their crew numbered 45 officers and enlisted men.

For surface running, the boats were powered by two 675 bhp diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 400 hp electric motor. They could reach 14 kn on the surface and 7.5 kn underwater. On the surface, the Sirena class had a range of 5000 nmi at 8 kn; submerged, they had a range of 72 nmi at 4 kn.

The boats were armed with six 53.3 cm torpedo tubes, four in the bow and two in the stern for which they carried a total of 12 torpedoes. They were also armed with a single 100 mm deck gun forward of the conning tower for combat on the surface. The anti-aircraft armament consisted of two or four 13.2 mm machine guns.

Construction and career
Smeraldo was laid down by Cantieri navali Tosi di Taranto at their Tarantoshipyard in 1931, launched on 27 July 1933 and completed the following year.