You are out on the water in foggy conditions. you hear one pronlonged blast plus two short blasts every two minutes. what should you do?

First, of all we should always accompany some one when we are walking through a foggy area. As it may be very beneficial to have another person along us. Along with that if we hear one prolonged blast plus two short blasts, then we must not lose our nerves as there is always a need for a more active body mechanism or system to be more responsive in nature.But, one should be very aware of  the different factors like he or she may have lost there way into the dockyard or they can be on the track to a restricted area because people are unable to see through the foggy space. But, there can be different reasons for such sounds.

where is the passage?

can't without the passage.

post the full question.

could you give me the options ?