Under which rule must vessels display day shapes to indicate their operational status?

Vessels are required to display day shapes to indicate their operational status under Rule 33, which pertains specifically to the signaling of vessels engaged in certain activities. This rule outlines the day shapes that must be shown during daylight hours, allowing other vessels to recognize the operational condition of the displaying vessel, whether it is engaged in fishing, towing, or is restricted in its ability to maneuver.

Having the correct day shapes visible is crucial for safe navigation. These shapes serve as visual indicators that communicate vital information to other mariners, enabling them to make informed decisions when approaching or navigating near the operational vessel.

In contrast, the other rules mentioned focus on different aspects of marine navigation and signaling, such as the rules for fishing vessels, sailing vessels, and vessels restricted in their ability to maneuver. While they all serve important purposes, Rule 33 is specifically aimed at the use of day shapes to indicate a vessel’s status during daylight, making it the correct choice.