What is the meaning of three long blasts followed by two short blasts on a ship's horn?

Three long blasts followed by two short blasts on a ship's horn typically signify that the vessel is preparing to leave a dock or berth. This sound pattern is part of the International Regulations for Preventing Collisions at Sea (COLREGs) and is used to communicate intentions to other vessels in the area. It serves to alert nearby boats and ensure safety during maneuvers.