What to do in an emergency – at sea

​VHF distress calls

A distress call is the most serious level of emergency. It applies to any situation where a person is threatened by grave and imminent danger and requires immediate assistance.

If you are at sea and use your mobile phone to make a 999 / 112 call, the Coastguard is unable to fix your position, so you should always use your VHF radio or DSC (as detailed below).

Making a distress call by voice (via VHF radio)

When using your VHF radio to make a distress call you must prefix the call with ‘Mayday’ so that we can identify it as an emergency call for help. A distress call has priority over all other transmissions.

A mayday call should be sent on VHF channel 16 using the following procedure:

  1. check the main battery switch is on to ensure there is electrical power to the VHF
  2. switch the VHF radio set on and select the high power setting
  3. select channel 16
  4. press and hold down the transmit button and say slowly and distinctly:

Mayday, mayday, mayday

This is *** (speak name of boat 3 times) the boat’s call sign and the MMSI number if you know it (spoken once)

Mayday *** (speak name of boat once)

My position is *** (latitude and longitude, or true bearing and distance from a known point)

Nature of distress (sinking, on fire etc.)

Help required (immediate assistance)

Number of persons on-board

Any other important information (eg drifting, flares, life raft available)


On completion of the distress call, release the transmit button and listen. If you do not receive an acknowledgement after approximately one minute, check the VHF set and repeat your distress call.

If you hear a distress call on your VHF radio, write down the details. If you can help, you should acknowledge accordingly, but only after giving an opportunity for the Coastguard station or some larger vessel to do so.

Making a distress call using DSC

All new VHF radios on sale are now equipped to make and receive DSC (Digital Selective Calling).

If you have a VHF DSC radio aboard you should have an MMSI (Mobile Maritime Service Identity), a 9 digit code number.

The MMSI number should be interfaced with your GPS (Global Positioning System). You should be familiar with its use and have the necessary licence requirements.

Using the procedures and switches applicable to your particular VHF DSC radio, a DSC distress alert might be sent as follows:

  • Momentarily press the (red, guarded) distress button. The VHF unit automatically switches to channel 70 (DSC distress channel) and transmits a basic distress alert with position and time (from GPS). The VHF unit then ensures it is set to channel 16
  • If time permits, select from the DSC menu the nature of the distress (eg fire), then press and hold the distress button for five seconds to send a full distress alert (or to the manufacturer requirements to operate)
  • Once received, the Coastguard sends a distress acknowledgement back on channel 70 before replying on channel 16. If a distress acknowledgement is not received from the Coastguard, the distress alert will be repeated automatically every four minutes

When a DSC distress acknowledgement has been received, or after about 15 seconds, the vessel in distress should transmit a mayday message by voice on channel 16, ensuring the MMSI number is part of the distress call.

If a distress alert is inadvertently transmitted, an ‘All Stations’ DSC message cancelling the false alert (by date and time) must be sent at once. Format of message:

  • All stations, all stations, all stations
  • This is *** (speak name of boat three times) and ********* (MMSI number once)
  • Cancel my DSC alert, sent in error
  • This is *** (speak name of boat once) and ********* (MMSI number once)
  • Over

Making a 999 / 112 call from shore

If you see a marine incident from the shore, you should dial 999 or 112 and ask for the coastguard.

You will be asked to report on the incident and may need to stay in telephone contact for further communications.