What indicates a vessel's intention to maneuver or change direction?

The correct answer highlights the fact that sound signals are an important form of communication on the water, especially in situations where visual cues may not be sufficient due to fog, rain, or other visibility impairments. Sound signals, such as a horn or whistle, are standardized in maritime navigation to convey a vessel's intentions, such as turning or overtaking another vessel. For instance, a series of short blasts may indicate that a vessel is about to alter its course, which is crucial for maintaining safety and awareness among nearby vessels.

Visual indicators like lights and flags can be ambiguous, particularly in poor visibility, making sound signals a reliable method for informing others of a ship's intended maneuvers. This understanding is key for mariners and is integrated into navigational rules to foster safe vessel operation in various maritime environments.