Ametista was the lead ship of her class of a dozen submarines, the second sub-class of the 600 Series of coastal submarines built for the Italian: [[Regia Marina]] (Royal Italian Navy) during the early 1930s.
The Sirena class was an improved and enlarged version of the preceding s. They displaced 680LT surfaced and 837LT submerged. The submarines were 61.5m (201.8feet) long, had a beam of 5.7m (18.7feet) and a draft of 4.7m (15.4feet). Their crew numbered 45 officers and enlisted men.[1]
For surface running, the boats were powered by two 6750NaN0 diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 400hp electric motor. They could reach 14kn on the surface and underwater. On the surface, the Sirena class had a range of 5000nmi at ;[1] submerged, they had a range of 72nmi at .[2]
The boats were armed with six 53.3cm (21inches) 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. Their anti-aircraft armament consisted of two or four 13.2adj=onNaNadj=on machine guns.[1]
Ametista was laid down by Odero-Terni-Orlando (OTO) at their Muggiano, La Spezia shipyard in 1931, launched on 24 April 1933 and completed the following year.[1]
. Chronology of the War at Sea 1939–1945: The Naval History of World War Two. Naval Institute Press. Annapolis, Maryland. 2005. Third Revised. 1-59114-119-2. Jürgen Rohwer.