What shapes should a vessel constrained by her draft display?

A vessel constrained by her draft is required to display a specific day shape as part of the International Regulations for Preventing Collisions at Sea (COLREGs). The correct shape is a cylinder-shaped day shape that is colored black, which is used to indicate that the vessel's ability to maneuver is limited due to its draft.

The rationale behind this requirement is to provide clear visual signals to other vessels about the specific navigation circumstances of the constrained vessel. A black cylinder is universally recognized within maritime navigation to signify this particular restriction, ensuring safety and aiding in collision avoidance.

While other shapes and colors may be associated with different types of vessels or situations, it is the black cylinder that correctly identifies a vessel constrained by its draft. This vital information helps other vessels understand its limitations and navigate accordingly in order to prevent collisions.