Question 508 Rules of the Road

The correct answer is C) southwest (225°). According to the International Regulations for Preventing Collisions at Sea (COLREGS), if you observe a vessel's red sidelight on your port beam, it means the vessel is traveling in a direction between 112.5° and 247.5° relative to your own course, which includes the southwest (225°) direction. The other options are incorrect because a vessel with its red sidelight visible on your port beam cannot be heading northeast (045°) or northwest (315°), as these directions would place the vessel's red sidelight on your starboard side. The vessel also cannot be heading southeast (135°), as this would place the red sidelight directly ahead of you, not on your port beam.