Sound Signals Used to Alert or Warn

Sound signals let other boaters know where you are located during periods of restricted visibility, such as extreme fog. If you hear the fog signal of a vessel you cannot see, slow to a minimum speed until you are sure there is not a risk of collision.

• One prolonged blast at intervals of not more than two minutes is the signal used by power-driven vessels when underway.
• One prolonged blast plus two short blasts at intervals of not more than two minutes is the signal used by sailing vessels.

Sound signals are used to warn other boaters or alert them to danger.

• One prolonged blast is a warning signal (for example, used when coming around a blind bend or leaving the dock).
• Five (or more) short, rapid blasts are used to signal danger or to signal that you do not understand or you disagree with the other boater’s intentions.