A vessel is towing a partly submerged object whose breadth is greater than 25m. How should it be lit?

The correct way to light a vessel towing a partly submerged object that has a breadth greater than 25 meters is to use two towing lights. According to the International Regulations for Preventing Collisions at Sea (COLREGs), when a vessel is towing, it must display specific lights to signal its presence to other vessels. For a towing operation involving a tow that is wider than 25 meters, two towing lights positioned vertically must be displayed at the stern of the towing vessel.

The use of two towing lights helps to adequately indicate the extent and nature of the tow to other vessels, enhancing safety during nighttime operations or in reduced visibility conditions. This guideline is in place to ensure that other vessels can recognize the tow's dimensions and understand that the object being towed is a separate entity, minimizing the risk of collisions.

In situations where a vessel is towing objects of various sizes or configurations, proper lighting is essential for navigation safety. The other choices do not meet the specific requirements set forth in COLREGs for this scenario.