Interwar submarines should not be judged as if they were intended to remain submerged for an entire patrol. These were surface-running submersibles that dived mainly to make attacks, so their hull forms had to work above water as well as below it. Snorkels and air-independent propulsion later extended submerged endurance, while nuclear power enabled truly long-range underwater operation. American boats could achieve great patrol radius before that transition, but they did so by carrying fuel for long surface passages. Their apparently unstreamlined hulls make sense once this operating cycle is understood.
Notable Point · 27:55-30:07
Interwar submarines were surface-running boats
Interwar boats spent most of a patrol on the surface, so their hulls and endurance should not be judged by the standards of later underwater submarines.