The description of First World War submarines as submersible torpedo boats concerns how they operated. They spent much of their cruising time on the surface, where their range was substantially greater than underwater. Surface cruising therefore supported the distances and operations required with the technology available. Minelaying was another useful role for these submarines.
Notable Point · 8:59-9:25
First World War submarines as submersible torpedo boats
Surface cruising and limited underwater endurance explain the description of early submarines as submersible torpedo boats.