What are the restrictions during innocent passage for submarines?

During innocent passage, submarines are required to surface and cannot engage in military exercises. This is significant because innocent passage allows a vessel to navigate through the territorial sea of another state, but such passage must be conducted in a manner that is not prejudicial to the peace, good order, or security of the coastal state.

By surfacing, submarines demonstrate their intent to comply with the legal requirements of innocent passage, which helps ensure transparency and minimizes potential misunderstandings or confrontations with the coastal state. Additionally, the prohibition on engaging in military exercises during this time further emphasizes the goal of maintaining good relations and ensuring that the passage does not appear threatening to the coastal state.

In contrast, remaining submerged (as suggested in another option) would violate the principles of innocent passage as it could be perceived as a means of evasion or hostility, while concerns about navigation using visual aids or staying in deeper waters do not pertain directly to the core requirements associated with the legal stipulations involved in innocent passage for submarines.