BOTH INTERNATIONAL & INLAND Vessel "A" is underway and pushing ahead when vessel "B" is sighted off the starboard bow as shown in illustration D028RR below. Which vessel is the stand-on vessel?

Correct Answer: Option D — Vessel "B" is the stand-on vessel because it is to starboard of vessel "A".

Rule 15 governs crossing situations. Vessel B is approaching on the starboard bow of Vessel A, making Vessel B the stand-on vessel and Vessel A the give-way vessel obligated to keep clear.