If you sound one short blast as a passing signal while meeting another vessel head-on and the other vessel responds with two short blasts, what should you do next?

When a vessel sounds one short blast while meeting another vessel head-on, it indicates the intention to pass on the port side. If the other vessel responds with two short blasts, this signifies that they intend to pass on the starboard side. In this situation, it indicates that there is a risk of collision due to the failure to agree on the passing arrangement.

In response to the two short blasts, the appropriate action is to sound the danger signal, which is typically five short blasts. This signal warns the other vessel of the potential danger of a collision, emphasizing the uncertainty and necessity for caution in the narrow passage situation.

Upon sounding the danger signal, the next actions may include evaluating the situation and potentially altering course or speed to avoid a collision, but the immediate response to the other vessel's two blasts is to send a clear message acknowledging the risk involved.