Underway at night, if you see the red sidelight of a vessel well off your port bow, which statement is TRUE?

Seeing the red sidelight of a vessel off your port bow indicates that the other vessel is approaching from your left side. According to the navigation rules, if you see this light and it is well off your bow, it generally means that the other vessel is not on a collision course with you. Therefore, you are not required to take action, meaning you may maintain your course and speed as long as there is no risk of collision.

Maintaining your course and speed is valid as long as you are not obstructing the other vessel's navigation or creating a hazard. When vessels have a clear understanding of their respective trajectories and distances, they can often pass without needing to alter course or speed.

This highlights the importance of situational awareness and understanding the rules regarding navigation lights and their implications on vessel movement at night.