Secret Fairway (1986)

The year 1944... The year of the victorious turning point in the WWII, but the Baltic theater of naval battles is still quiet. While performing a combat mission, torpedo boat commander Boris Shubin accidentally discovers a secret fairway of an unmarked German submarine. Unforeseen chance throws him on the "Flying Dutchman" and gives him the opportunity to open the veil of the strictest secrecy of the Third Reich, which surrounds her....