The Sirena-class submarines were the second sub-class of the 600 Series of coastal submarines built for the (Royal Italian Navy) during the early 1930s. Of the dozen boats built of this class, only one survived World War II.
The Sirena class was an improved and enlarged version of the preceding s. They displaced surfaced and submerged. The submarines were long, had a beam of and a draft of . Their crew numbered 45 officers and enlisted men.
For surface running, the boats were powered by two diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the Sirena class had a range of at ; submerged, they had a range of at .
The boats were armed with six 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 deck gun forward of the conning tower for combat on the surface. The anti-aircraft armament consisted of two or four machine guns.
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