Final answer:
A vessel constrained by draught exhibits three black balls in a vertical line during the day and three all-round red lights in a vertical line at night, in addition to its normal navigation lights, to indicate its limited maneuverability due to its deep draught.
Step-by-step explanation:
Identification of a Vessel Constrained By Draught
A vessel constrained by draught is a large ship that due to its deep draught in relation to the available depth of water is severely restricted in its ability to deviate from its course. According to the International Regulations for Preventing Collisions at Sea (COLREGs), a vessel constrained by draught must exhibit lights or shapes to signal its status to other vessels, particularly when navigating waters where the depths restrict its safe maneuverability. During daylight hours, such a vessel must display three black balls in a vertical line where they can best be seen.
At night time, the vessel displays three all-round red lights in a vertical line, in addition to the standard masthead lights, sidelights, and a stern light that power-driven vessels are required to exhibit. This signal informs other vessels that due to the constrained vessel's deep draught, it is unable to get out of the way and should be approached with caution, and that other vessels should give it a wide berth. While these lights and shapes are specific to vessels constrained by draught, it's essential for all seafarers to recognize and understand the lighting configurations of various vessels to ensure safety and compliance with maritime navigation rules.