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

During a foggy condition, visibility is typically reduced. In a fog condition, if one hear one prolonged blast plus two short blasts every two minutes, the sound signals that a vessel is under sail, that is, a sailing vessel is underway.

If I hear one prolonged blast plus two short blasts every two minutes, then it means that a vessel is sailing. These sound signals are used to alert the nearby vessels, that this vessel is sailing. Motorboats have to give one prolonged blast every two minutes.