What must a give-way vessel do according to the rules?

A give-way vessel is required to take early and substantial action to keep clear of the stand-on vessel. This means that when a vessel is identified as the give-way vessel in a potential collision situation, it has the responsibility to maneuver in a way that ensures the safety of both itself and the stand-on vessel. This could involve altering course, changing speed, or both, but the actions must be clear and decisive to avoid confusion or accidents.

Taking early action is crucial to prevent a potential collision, and the term "substantial" emphasizes that the maneuvers should be significant enough to effectively maintain safe distances from the stand-on vessel. The rules emphasize proactive measures to promote safety on the waters, acknowledging that while the stand-on vessel has a duty to maintain its course and speed, it is the responsibility of the give-way vessel to take action.

The other alternatives, such as waiting for the stand-on vessel to move or changing course unpredictably, could result in misunderstandings and potentially dangerous situations. Matching the speed of other vessels does not inherently address the need for separation between vessels when one is required to give way, and instead focuses on the flow of traffic, which is a separate consideration in navigation rules.