When must the rules regarding shapes be adhered to?

The rules regarding shapes must be adhered to at day because these shapes serve as a means of visual communication between vessels during daylight hours. The International Regulations for Preventing Collisions at Sea (COLREGs) specify the use of shapes, such as flags, to indicate the type of vessel, its activity, and its status.

During the day, mariners rely on these visual signals to ensure safe navigation and to understand the intentions of nearby vessels. Shapes communicate important information, such as whether a vessel is anchored, aground, or in tow. This visual signaling is essential for collision avoidance during daylight when visibility allows for these shapes to be seen.

While shapes are still relevant at night, the use of lights takes precedence, and the compliance with shapes is not as critical during nighttime operations. In conditions like fog, vessels may rely more on sound signals or radar, and the same applies at sunset, where visibility may be compromised, further underlining the importance of shapes during daylight hours when they can be clearly observed.