What must vessels that are unpowered and less than 23 feet long carry if exhibiting practical navigation lights isn’t possible?

Vessels that are unpowered and less than 23 feet long are required to carry a lantern or flashlight emitting a white light when exhibiting practical navigation lights is not feasible. This requirement ensures that even in the absence of fixed navigation lights, the vessel can still be visible to others on the water, especially during low-light conditions or at night. The white light serves as a clear indication of the vessel's presence, helping to prevent collisions and enhancing safety for both the vessel and other boaters.

The other options do not fulfill this specific legal requirement. Extra batteries can be useful for maintaining powered lights but do not serve as a substitute for navigation lights. A handheld radio can facilitate communication but does not contribute to visibility in the dark. A signaling mirror might be useful in daylight for signaling but would not provide the illumination needed to ensure visibility during nighttime or low-light situations. Therefore, carrying a lantern or flashlight that emits white light is essential for complying with navigation safety regulations for unpowered vessels.