What does "22.5 degrees abaft her beam" indicate about the overtaking vessel's position?

Answer: B — The overtaking vessel is able to see only the sternlight of the vessel

"22.5 degrees abaft her beam" refers to the relative position of an overtaking vessel in relation to the vessel being overtaken. This specific angle indicates that the overtaking vessel is positioned off the wake of the vessel it is passing, more towards the stern than the beam. When the overtaking vessel is within 22.5 degrees from the stern of the vessel being overtaken, it means that the overtaking vessel will only be able to see the sternlight of the vessel being overtaken. This visibility confirms that the overtaking vessel has not yet passed the other vessel and is still approaching from behind. Understanding this aspect of the navigation rules is crucial. When a vessel is overtaken, the overtaken vessel should only see the sidelights and possibly the masthead lights of the overtaking vessel once it is sufficiently ahead. Therefore, the scenario presented aligns with the visibility rule that specifies the other vessel's sternlight would be visible when the overtaking vessel is within that specific angle.