You are the stand-on vessel in a crossing situation. Which signal should you sound if you think the give-way vessel is NOT taking sufficient action to avoid collision?

In a crossing situation where you are identified as the stand-on vessel, if you believe that the give-way vessel is not taking adequate measures to avoid a collision, the appropriate signal to sound is five short and rapid blasts. This sound signal is universally recognized as a warning, indicating that you are unsure of the other vessel's intentions or actions and are concerned about a potential collision.

This signal effectively conveys urgency and alerts the other vessel to your concerns, prompting them to reassess their maneuvers and take necessary actions to ensure safe navigation. It is an essential communication tool within the Rules of the Road, enabling vessels to convey their status and intentions clearly when visual cues alone may not suffice.

The other options serve different purposes within the context of the navigational rules and would not be appropriate in this specific scenario. For instance, a prolonged blast typically denotes the intent to overtake or may indicate the presence of a vessel maneuvering in limited visibility. Meanwhile, shorter blasts have different meanings related to specific maneuvers or actions.