Armor and passive protection against small drones

Could sea and aerial drones bring back torpedo defenses or belt armor?

Some passive protection may return, especially outer skins and barriers that reduce the effect of cheap drones.

Small explosive drones may make additional passive protection worth considering. Torpedo nets, a little armour, and an outer skin around the main hull are suggested as possible ways to reduce damage. The expectation is mitigation, especially against cheaper systems, rather than a guarantee of protection. If those measures make low-cost weapons less effective, an attacker would have to spend more to obtain the same result.