Question 983 Rules of the Road

The correct answer is D) A towing vessel. The signal of one prolonged blast followed by two short blasts is the sound signal prescribed in the International and Inland Navigation Rules to indicate that a vessel is towing another vessel or object astern. This signal alerts other vessels in the area that the towing vessel and its tow are present and maneuverability may be restricted. The other answer choices are incorrect because they do not match the sound signal described in the question. A vessel engaged on pilotage duty, a vessel stopped and making no way through the water, and a vessel aground in a fairway would have different sound signals prescribed in the navigation rules.