The ARGO in Cagliari (Sardinia) upon its return to the Mediterranean Sea from Bordeaux.
(Photo courtesy Erminio Bagnasco and Achille Rastelli)

The resistant, or pressure hull of the ARGO. Note the steel plates were riveted to cylindrical beams, and how the hull decreased in diameter toward the ends.
(Photo Turrini)

Monfalcone, November 24th, 1936: the launch of the ARGO.
(Photo Turrini)

The submarine FLUTTO. The TRITONE class is referred to by some authors as the FLUTTO class..
(Photo courtesy Erminio Bagnasco and Achille Rastelli)

The hulls of the FLUTTO and VORTICE..
(Photo Turrini)

The MAREA (Left) in Bermuda along with the ONICE in summer 1944..
(Photo courtesy Erminio Bagnasco and Achille Rastelli)