This one long blast serves as a warning to other craft that there is an unseen vessel in the area. Be on alert!
The sound signal short-long-short is an optional, additional signal made by a vessel at anchor in restricted visibility. The signal may be made by such a vessel in addition to her required sound signal to give warning of her position and of the possibility of collision to an approaching vessel.Collision Regulations 35(g)
Two short horn blast from a vessel means that she is turning port and one short horn blast that she is turning starboard
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?
On seagoing vessels in restricted visibility a prolonged blast on the ships whistle means the vessel is making way through the water.
one prolonged blast
B
Vessel operators can alert the lock attendant of their request to transit through the lock by sounding one prolonged blast followed by one short blast
one prolonged blast
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.
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.