You are out on the water in foggy conditions you here one prolonged blast plus 2 short blasts every two minutes what does this sound signal mean?

The sound signal of one prolonged blast followed by two short blasts every two minutes indicates that a vessel is restricted in its ability to maneuver. This signal is used to alert other vessels in the area of the restricted vessel's presence, especially in low visibility conditions like fog. It is important for nearby vessels to be cautious and maintain a safe distance from the restricted vessel.