Final answer:
If you only see a green light while boating at night, it indicates the starboard side of another vessel, typically a sailboat, and you need to yield the right of way to avoid collision.
Step-by-step explanation:
If you see only a green light while boating at night, you may be approaching a sailboat, and you must yield the right of way. This is because, according to the navigation rules, a green light indicates the starboard side of another vessel, and if you only see the green light, it means you are approaching the vessel from a crossing position on its port (left) side. In such a situation, you would generally be the give-way vessel and would need to take action to avoid a collision. It is crucial to remember these rules to ensure safety on the water.