They intend to pass starboard side to starboard side.
The Vessel is turning to Starboard .
You are operating a motorboat. You hear one prolonged blast from the horn of another vessel. What should you do?
B
there is a dangerous situation
One prolonged blast from the horn of another vessel indicates reduced visibility (and the presence of that vehicle). The reduced visibility may be due to geography, such as a river with significant bends, or weather features, such as fog.
In reduced visibility, it means the presence of another watercraft.
Two short horn blast from a vessel means that she is turning port and one short horn blast that she is turning starboard
Rules of the Road.Rule 35InternationalSound Signals in Restricted visibility.(c) A vessel not under command, a vessel restricted in her ability to maneuver, a vessel constrained by her draft, a sailing vessel, a vessel engaged in fishing, and a vessel engaged in towing or pushing another vessel shall, instead of the signals prescribed in paragraphs (a) or (b) of this rule, sound at intervals of not more than two minutes three blast in succession, namely one prolonged followed by two short blast.
Rule 34International:" I AM altering my course to port."Inland: " I INTEND to leave you on my starboard side or I AGREE to a starboard to starboard passing or I INTEND to overtake you on your portside."They intend to pass starboard to starboard side.
Assuming you are referring to a fog horn or a warning signal, generally find where the other vessel is and change course accordingly
Rules of the Road. Rule 35, Sound Signals in Restricted Visibility. (C) A vessel not under command, a vessel restricted in her ability to maneuver, a vessel constrained by her draft, a sailing vessel, a vessel engaged in fishing, and a vessel engaged in towing or pushing another vessel SHALL, sound at intervals of not more than two minutes three blast in succession, namely one prolonged followed by two short blast.
In the maritime environment, it mean several things: 1. In restricted visibility it means the vessel is making way through the water. 2. A vessel approaching a blind bend in a river can sound one prolonged blast on the ships' whistle to alert any other vessels to its presence, if another vessel is nearby then they will respond with one prolonged blast on the ships' whistle.