Boat sound signals: How to respond to a ship’s horn

If you’re somewhere like Sydney Harbour where boats of all sizes are constantly plying the waterways, recognising and understanding sound signals can be a big help, not only for larger boats but for you.

By law, every boat on NSW waters must carry a sound signal device that can be as simple as a whistle.

But what are the sound signals, and what do they mean? 

If you hear one short horn, it means the boat approaching you and sounding the horn is going to turn to starboard (right), meaning you also will have to turn to starboard to avoid a collision.

If you hear two short horns, it means the boat approaching you and sounding the horn is going to turn to port (left), meaning you also will have to turn to port to avoid a collision.

If you hear three short horns, it means the boat approaching you is slowing or stopping, usually by putting its engines into reverse. In this instance, you’re going to have to treat the boat making the sound signal as an obstacle and set your course around it.

This is an important one. If the boat approaching you makes five short blasts of its horn, it means the skipper is unsure about what you’re going to do. The best response here is to make a clear change in your course to show the boat making the sound signal that you are attempting to get out of the way.

If you’re a regular visitor to inland waterways with snaking rivers, you’re probably familiar with this one.

River bends can be hard to see around if there is a high riverbank or trees lining them, and the water tends to be deeper on the outside of a river bend than inside it, meaning not the entire width of the river is navigable.

To minimise the risk of meeting an oncoming boat when approaching a bend in the river, a boat can make one long sound signal to let boats coming the other way know that they are about to meet with oncoming traffic.

There’s nothing as scary as being out on the water in a complete white-out, where you can only see a short distance away from the boat.

If you’re in a power boat and moving or anchored, you should be giving a single long blast of a horn at regular, short intervals of no more than two minutes to alert other boats that you’re in the area. If you’re in a sailboat, the convention is that you make one long blast followed by two short blasts to indicate powered boats will need to give way to you.

The simplest form of sound signal to use is a whistle. If you want to use a whistle with a pea in it, make sure the whistle has been made to use in marine environments as the pea may become stuck, reducing the effectiveness of the whistle.

You can also buy special pealess whistles that are designed to be extra loud.

Another effective handheld solution is to have an air horn. These come in several different forms, such as a trumpet, a hand-pumped air horn, and one that uses compressed air.

For those who want ease of use, a boat can be equipped with an electric horn.

Smarter VHF radios fitted to boots can also include a PA function that can either make sound signals at the push of the mic button or automatically broadcast a foghorn at regular intervals.

The minimum distance that boats can pass without having to slow to 5.0 knots varies from 30 to 50 metres depending on where you are boating. make sure you check the local rules and regulations.

The larger the boat, the more careful you need to be if it is turning, as they tend to steer from the stern which swings out wide.

Note that if you are in a harbour where there are navy ships present, there are important restrictions on how closely you can approach them, either while they’re on the move or moored. Stay at least 60 metres away from the side of a moored or moving navy vessel, and at least 200 metres clear of its bow while it is underway.