What day shape is prescribed for a vessel constrained by her draft?

A vessel constrained by her draft is required to display a specific day shape that helps other navigators identify her limitations. The correct answer is the cylindrical shape because it indicates that the vessel's ability to maneuver is significantly restricted due to the depth of water she requires to navigate safely. This shape is universally recognized in maritime navigation and serves to enhance safety by clearly conveying important information about the vessel's operational capabilities.

In contrast, the other choices represent different characteristics or restrictions of vessel movements. For instance, a black cone apex upward indicates a vessel not under command, while a black cone apex downward suggests a vessel aground. Two vertical black balls signify a vessel anchored. Each of these shapes communicates a different status or limitation of a vessel's navigation, but the cylindrical shape is specifically designated for vessels constrained by their draft. Understanding these day shapes is crucial for ensuring safe navigation in crowded or narrow waterways.