CINEGIORNALI DI GUERRA: No.1, September 1939 - May 1940
This is the VHS release (see more).
SummaryTape No.1 contains two sub-related episodes:
1.) La Spezia: Esercitazioni di Sommergibili
Excellent interior and exterior footage on an Italian ocean-class sub on training exercises.
2.) Mare del Nord: I Sommergibili Germanici
German U-boats training with their own destroyers.