From the USCG Navigational Rules of the Road (International and Inland.)
Rule 34
Maneuvering and Warning Signals
(d) When vessels in sight of one another are approaching each other and from any cause one fails to understand the intentions or actions of another, or is in doubt whether sufficient action is being taken by the other to avoid collision, the vessel in doubt shall immediately indicate such doubt by giving at least 5 short and rapid blasts of the ships whistle.
From the USCG Navigational Rules of the Road (International and Inland.)
Rule 34
Maneuvering and Warning Signals
(d) When vessels in sight of one another are approaching each other and from any cause one fails to understand the intentions or actions of another, or is in doubt whether sufficient action is being taken by the other to avoid collision, the vessel in doubt shall immediately indicate such doubt by giving at least 5 short and rapid blasts of the ships whistle....
one prolonged blast
There is no such thing as a "long blast", it is called a "prolonged" blast lasting between 4-6 seconds.-If you agree with the arrangement you would sound the same signal, then take the necessary steps to effect a safe passing. If there is any doubt though the danger signal of five short needs to be sounded.ETA: Rules of the Road, Rule 34-internationalA.) One Short blast means "I am altering my course to Starboard."Two Short blasts mean "I am altering my course to Port."Rule 34-InlandA.)One short blast means "I intend to leave you on my port side."Two short blasts means " I intend to leave you on my starboard side."
If a boater sounds five short blasts using a horn or whistle, it typically indicates danger or an intention to communicate that they are unsure of another vessel's intentions. This signal is often used in situations where visibility is poor or when the boater feels that their safety is at risk. It's a standard maritime communication signal outlined in the International Regulations for Preventing Collisions at Sea (COLREGs).
Don't know what it means, but five short blasts from the hoRN must be a warning of some kind?
Signal by radio on channel 9, 13 or 16 - "(name of bridge times three", this is (boat name), requesting your schedule or on demand opening. Alternatively you can signal with a four second blast followed by a short blast. He will either signal back the same or signal "no" with five short blasts. If he signals no you must reaping in kind to acknowledge.
I intend to pass you on my port (left) side.It means I intend to LEAVE you on my port side. That means you will be overtaking the vessel you are approaching (which is the stand on vessel and has the right away) and leaving it on YOUR port side. Simply put you are over taking the vessel and maneuvering to your right. If you are passing from behind and the other vessel is in agreement they will sound the same sound, one short blast. To pass on the opposite side leaving them on your starboard side then you will sound two short blasts. If in agreement you will hear two short blasts in return.
4 short blasts are the letter H is morse. On the River Clyde in Scotland a local bye law allows it to be signalled by a vessel going astern from a berth, generally a paddle steamer, indicating that it is going astern, it has difficulty in manoeuvring and warning other vessels to keep clear.
There are particular sound signals that are to be used when you first get underway. One prolonged blast signifies that you are about to get underway. If you are going to make way in reverse, you need to signal an additional 3 short blasts.
From the USCG Navigational Rules of the Road (International and Inland.)Rule 34Maneuvering and Warning Signals(d) When vessels in sight of one another are approaching each other and from any cause one fails to understand the intentions or actions of another, or is in doubt whether sufficient action is being taken by the other to avoid collision, the vessel in doubt shall immediately indicate such doubt by giving at least 5 short and rapid blasts of the ships whistle.
It means "Man overboard". Note: 1 long blast = 5 or 6 seconds 1 short blast = 1 or 2 seconds Three short blasts means "My engines are going Astern". (It doesn't necessarily mean that the ship itself is going astern).
Five short blasts on a horn in boating typically signal a warning or indicate that a vessel is unsure of another vessel's intentions, often in situations of restricted visibility or when navigating in close quarters. It can also mean that a vessel is backing up or has an emergency situation. This sound signal is part of the International Regulations for Preventing Collisions at Sea (COLREGs) and is important for maintaining safety on the water.
When vessels in sight of one another are approaching each other and from any cause either vessel fails to understand the intentions or actions of the other, or is in doubt whether sufficient action is being taken by the other to avoid collision, the vessel in doubt shall immediately indicate such doubt by giving at least five short and rapid blasts on the whistle