What does 11 prolonged blast mean?

An "11 prolonged blast" typically refers to a signal used in maritime communication, particularly in fog or low visibility conditions. It consists of a series of 11 long blasts on a ship's horn, indicating the vessel's presence to others in the vicinity. This signal is part of the International Regulations for Preventing Collisions at Sea (COLREGS), ensuring safety and awareness among vessels. It serves as a warning to nearby ships that the vessel is either maneuvering or requires caution due to its operational status.