While operating in a narrow channel, another vessel crosses from starboard to port and you are uncertain of its intentions. What action may you take?

Sounding the danger signal is appropriate when you are uncertain of another vessel's intentions and there is a potential risk of collision. The danger signal, which consists of five short blasts on the whistle, is a way to communicate to other vessels that you perceive a dangerous situation. By using this signal, you alert the other vessel to your concerns regarding safety and encourage them to take appropriate action to avoid a collision.

Understanding the context of navigation rules is crucial in operating within narrow channels, where the risk of collision is higher and the actions of other vessels can be unpredictable. The danger signal serves as a means to avert a potential accident while allowing other operators to gauge the situation and respond accordingly.