During the daytime, a diving vessel must exhibit the international code flag of which size?

The correct answer is based on the International Regulations for Preventing Collisions at Sea (COLREGs) and the specific lighting and marking requirements for vessels engaged in diving operations. According to these regulations, a vessel engaged in diving activities must display the international code flag 'A' (the alpha flag) during the day.

For a diving vessel, the flag must be of a specified minimum size to ensure it is visible from a distance. The requirement for the diving vessel to have a flag that is at least 1 meter in diameter is established to ensure that the flag can be easily recognized by other vessels in the vicinity, promoting safety by alerting them to the presence of divers in the water. This visibility is crucial, especially to prevent accidents and to ensure that vessels maintain a safe distance from the dive site.

While larger flags can enhance visibility further, the 1-meter standard is a common requirement, thereby making it the answer regarding the minimum size for the flag on a diving vessel during the daytime.