When is a towing light required to be above the stern light?

A towing light is required to be above the stern light when a vessel is towing astern to ensure proper visibility and identification of the vessel's operation. This vertical positioning helps to indicate to other vessels that the towing vessel is engaged in a specific operation, distinguishing it from other types of navigation. The towing light serves as a signal, alerting other mariners to the possibility of a towed vessel being nearby and potentially extending beyond the stern of the towing ship.

In this scenario, the requirement for positioning the towing light above the stern light is crucial for safety on the water, particularly at night or in low visibility conditions. The distinction is important to prevent collisions by providing clarity on the vessel's configuration and activity.

In contrast, when a vessel is at anchor or moored, it does not require a towing light, as it is not engaged in towing operations. The need for a light during daylight is also irrelevant in this context, as the towing light's function might not be necessary; other markers or signals could maintain safety during such times. Thus, the context of towing operations is pivotal in determining the correct answer, which emphasizes proper signaling for maritime navigation.