Observe and identify

Developing level, about 2 min. International COLREGs / IRPCS.

The situation

A vessel ahead is showing a daytime shape. Inspect the shape and its vertical arrangement with the binoculars. The vessel’s name and status are withheld until your answer.

Which operation or status does this daytime signal indicate?

Restricted ability to manoeuvre
Aground
Not under command

Answers and explanations

Lookout: Ball–diamond–ball indicates restriction arising from the nature of the vessel’s work. Interpret her operation and the applicable encounter before deciding your duty.

The sound answer

Restricted ability to manoeuvre

Ball–diamond–ball indicates restriction arising from the nature of the vessel’s work. Interpret her operation and the applicable encounter before deciding your duty.

Why the other options fall short

Aground

Aground uses ball, ball, ball. The displayed signal here indicates restricted ability to manoeuvre. Ball–diamond–ball indicates restriction arising from the nature of the vessel’s work. Interpret her operation and the applicable encounter before deciding your duty.

Not under command

Not under command uses ball, ball. The displayed signal here indicates restricted ability to manoeuvre. Ball–diamond–ball indicates restriction arising from the nature of the vessel’s work. Interpret her operation and the applicable encounter before deciding your duty.

Rule 27(b) · Day shapes