What day shape indicates a vessel restricted in its ability to maneuver?

A diamond shape is used to indicate a vessel that is restricted in its ability to maneuver. This shape serves as a visual signal to other vessels, indicating that the particular craft may not be able to change course or speed easily due to its operational limitations, such as working gear, shallow draft, or the presence of tows that restrict its movements.

In maritime navigation, the use of specific shapes, colors, and lights as day shapes is crucial for safe navigation and to avoid collisions. Each shape conveys a distinct message about the status or capabilities of the vessel. The diamond shape is universally recognized in the International Regulations for Preventing Collisions at Sea (COLREGs) as the signal for vessels that cannot maneuver as easily as others, helping to alert nearby vessels to take the necessary precautions.

Other shapes indicate different statuses and conditions of vessels but do not apply to a restricted ability to maneuver. For example, signaling shapes like circles or triangles denote other conditions, such as vessels engaged in fishing or underway without power, which would not accurately represent a restricted maneuverability situation.