What flag is used by the ship with visual communication duty while in port?

The ship with visual communication duty while in port uses the Yankee flag. This flag signifies that the vessel is engaged in conveying information regarding its status and operations, particularly to ensure other vessels and shore commands are aware of its situation. The Yankee flag, which is a blue and yellow diagonal striped flag, is part of the International Code of Signals and indicates that the ship intends to communicate or has information to relay.

In contrast, the other flags mentioned serve different functions in maritime communication. Alpha signals diver and diver down, Bravo indicates that the ship is handling dangerous cargo, and Zulu relates to a ship being ready to receive alongside or conduct operations, but they do not pertain to visual communication specifically while in port. Understanding the function of these flags is key in recognizing the protocols and safety measures observed in maritime operations.