What is the minimum breadth at which a partly submerged object must display all-around white lights?

The minimum breadth at which a partly submerged object must display all-around white lights is 25 meters. According to the International Regulations for Preventing Collisions at Sea (COLREGs), specifically Rule 30, a partly submerged object of this size must be marked with all-around white lights to ensure visibility to other vessels. This requirement is essential for safety, as it allows other boat operators to see the presence of the object, which could pose a hazard, particularly at night or during poor visibility conditions.

For vessels or objects broader than 25 meters, the rule is enforced to improve navigational safety, allowing other vessels to maintain a safe distance. Thus, compliance with this regulation significantly reduces the risk of collisions and enhances the safety of navigation for all nearby vessels.