What shapes are exhibited by a vessel dredging and having an obstruction to port?

A vessel engaged in dredging must display specific shapes to indicate its activities and the nature of its operations to other vessels. When a dredging vessel has an obstruction to port, it is required to exhibit shapes that clearly signal its operational status and the direction of navigational hazards.

In this situation, the correct answer highlights the requirement to show three shapes in a vertical line. This configuration consists of two black balls above one diamond shape, which signals the presence of a dredging operation with a specific obstruction on the port side. The vertical arrangement of these shapes makes the signal more visible to other vessels from a distance and communicates that there is an obstruction to navigate around.

The other options describe arrangements or numbers of shapes that do not accurately represent the requirements set forth by the COLREGs for a dredging vessel in this scenario. The correct arrangement is crucial for safe navigation and awareness in waterways, ensuring that other vessels understand where the dredging operation is taking place and where they may need to take caution.