What precaution must vessels aground take as per Rule 26?

Answer: B — They must display specific lights and shapes indicating their status

Vessels that are aground must display specific lights and shapes to indicate their status, in accordance with Rule 26 of the COLREGs. This rule is designed to ensure that other vessels are made aware of a grounded vessel's situation so they can navigate safely around it and avoid potential collisions. The requirement typically includes a specific day shape, such as a ball, indicating that the vessel is aground, along with appropriate lights during the nighttime. This visual signaling is crucial for the safety of all vessels in the area, enhancing situational awareness and facilitating safe navigation. In contrast, reflective markers, anchoring with two anchors, or signaling every hour are not stipulated in Rule 26 as necessary precautions for vessels aground, making them unsuitable choices for this question. This clarity emphasizes the importance of proper signaling in maritime safety regulations.