The definition of distress in the 1979 Search and Rescue Convention is:

Grave and Imminent Danger to a Person, Ship, Aircraft or Other Vehicle Requiring Immediate Assistance.

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DISTRESS is announced using the word MAYDAY, derived from the French M'aidez, meaning "Help me". This prefix must only be used for distress traffic and, except in a distress situation, the word MAYDAY should never be used on the radio even in conversation. Emergencies that do not fall into distress category but where an urgent message needs to be passed concerning the safety of a person, ship, aircraft or other vehicle, ae used URGENCY messages prefixed PAN-PAN. Transmissions concerning the safety of navigation are prefixed SECURITE.

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It is important to send a DSC signal first when in an emergency situation, because  pertinent information like your vessel type, name and position is broadcasted digitally to all vessels in your VHF range vicinity which gains more accurate and faster response times. After the DSC alert, you should send a voice alert. 

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Distress transmission

There are three separate parts to a distress transmission:

A. The DSC Distress Alert

B. The Voice Distress Call

C. The Voice Distress Message

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Parts A,B and C used if DSC is fitted. Parts B and C if it is not. 

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To send a distress alert from the DSC you should:

1. Lift the cover of the RED distress button.

2. Press the RED distress button momentarily.

3. Select the Nature of Distress if times allows i.e. fire, sinking, collision, etc.

4. Depress the RED button for five seconds or until the apparatus informs you that the alert has been sent. The equipment will now automatically send a short electronic data burst on Ch70 giving:

a) your MMSI

b) your position (from GPS or manual entry)

c) time the distress alert was sent

d) the nature of distress (if selected)

5. The screen will indicate Ch16 - it is automatically tuned in preparation for voice communication. The whole process takes about 15 seconds.

6. The VHF DSC apparatus will repeat the distress alert approximately every four minutes until a digital acknowledgement is received on Ch70 or until the originating station cancels the alert. The screen will display the MMSI of the acknowledging station.

7. Wait 15 seconds and then give the voice Distress Call and Message. 

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The distress call

A distress call has absolute priority over all other transmissions. All stations hearing it must immediately cease any transmissions which could cause interference to the distress traffic. They must then continue to listen on the frequency for the distress message.

 

Mayday, Mayday, Mayday

Tis is sailing yacht Nafsika, Nafsika. MMSI (or call-sign if no DSC fitted). 

 

The distress message

The distress message follows the distress call without a break and should be spoken SLOWLY and CLEARLY. Remember that your rescuer will be trying to write down your position and other details. The internationally recognised format is:

Mayday Yacht Nafsika

Position (in Lat and Long or true bearing and distance from a prominent charted object)

Nature of distress (fire, sinking, hita submerged object etc.)

Assistance required

Total number of persons on board (important as it could affect the choice of rescue method)

Other useful information 

Over (awaiting a reply)

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The following is an example of a complete voice distress transmission following a DSC distress alert:

Mayday, Mayday, Mayday

This is sailing yacht Nafsika, Nafsika, Nafsika MMSI 234001234

Mayday sailing yacht Nafsika

My position is 50°46'N 001°17'W

Swamped in rough sea and sinking 

I require immediate assistance

Five people on board

Abandoning to liferaft

Over

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