World War I submarines normally cruised on the surface and submerged for concealment, bad weather, or a short attack. Their low underwater speed and endurance meant that merely forcing one to dive could prevent it from reaching a convoy or conducting a useful pursuit. They could use brief submerged runs to lay mines close to defended waters, but they could not wait or chase underwater for long. Aircraft and submarines illustrate how counters often evolve alongside a supposedly revolutionary weapon.
Chapter · 6:03-15:07
Why early submarines were vulnerable from the air
Early submarines are explained as surface-running torpedo boats whose limited underwater endurance made aircraft a natural counter.