Interwar diesel-electric boats cannot be judged by nuclear-submarine operating patterns. They spent much of their time on the surface because their surfaced endurance far exceeded their underwater range. They commonly moved at night, reached a patrol position, and submerged to wait like a mobile minefield. Features that look inefficient through a modern lens supported seakeeping and sustained surface operation in the environment for which the boats were built.
Notable Point · 20:53-22:19
Why interwar submarines were designed to live on the surface
Royal Navy boats made long passages and much of their tactical movement on the surface before submerging to ambush.