Everything you need to know about the basics of flags and signals

22nd February 2021

In years gone by sailors relied on long strings of flags, bells and horns to communicate. In this era of mobile phones, chart-plotters, navigation apps, the internet and handheld VHF radios, flags and signals seem increasingly quaint. And yet there are still many flags and signals that remain relevant in a digital world, and a total reliance on technology isn’t advised. There’s still nothing quite like looking out the window.   

While we recommend that you know the full range of safety lights and of course navigational signals, here are a few of the flags and signals that boaties are likely to find useful on the water:


Distress signal

Most commonly used in dinghy sailing but recognised internationally, slowly and repeatedly raising and lowering both of your outstretched arms is known as a distress signal, indicating that you require immediate assistance.

Diving flag

Be wary of the international code flag A as the small white and blue flag indicates that there are divers below. Boats should keep at least 50 metres clear of a diving flag or a boat displaying a diving flag.

Sound signals in fog 

Fog isn’t nearly as common in Australian waters as it is in many other parts of the world, however, it’s important that you know what to do if you do experience fog or reduced visibility in poor weather. Power boats should emit one long blast of a horn every two minutes. Sailing boats should use one long blast followed by two short blasts every two minutes.  

Manoeuvring sound signals

As well as fog sound signals, it is also useful to know a few basic manoeuvring sound signals that will help you navigate around large and commercial shipping. One long blast warns that the boat emitting the signal is leaving a dock or nearing an obstructed area or blind corner.

Three quick blasts signal that the boat’s engine is in reverse with the intent to stop or reverse the boat. One short blast indicates that the boat is altering course to starboard (right), and two short blasts indicate that the boat is altering course to port (left). Finally, five short blasts indicate that the boat is unsure of your intentions.    

Fishing or towing lights

Commercial fishing boats will show a red light over white, and commercial fishing boats undertaking trawling will display a green light over white. In addition to their normal navigational lights, vessels that are towing or are in some way restricted in their ability to manoeuvre will display a red light over a white light over another red light. Or, more simply, if something resembles a lit-up Christmas tree, steer well clear!

Quarantine flag

The bright yellow international code flag Q is known as the quarantine flag. Historically, the flag has been used to mark disease and would be flown by ships carrying passengers infected by plagues and other terrible diseases. But these days, yachts entering Australian waters are required to fly the flag until they’ve been formally cleared by quarantine officials. Until this has happened, other boats shouldn’t approach and should restrict their greeting to a friendly wave to the crew who have likely travelled across an ocean to reach Australian waters. 

Flags and signals are the same in every language, and if used effectively these simple acts of communication can offer assistance to someone in need.