First, let's be very clear that making a false distress call is a federal crime carrying sanctions of up to six years imprisonment, and a fine of $250,000.
Second, there is no commercial or maritime use of Morse now, so distress calls use "Mayday Mayday Mayday" at the beginning and end. You are extremely unlikely to hear a Morse distress call or need to respond to one. Maritime Morse stations stopped operation on July 12, 1999, almost twenty years ago.
When someone who is not a first responder or dispatcher receives a distress call, they need to start writing down information to forward to first responders. If they don't provide it, and they may be scared and not thinking straight, you need to interview them.
Be calm and clear. If a better-prepared station steps in to help, let them do it.
For a maritime distress call, collect this information. A land call would be similar. This is a script for the person making the call, so you would walk them through this.
First, write down the local time (your own clock). If you have UTC, use that.
- Distress signal "MAYDAY", spoken three times.
- The words "THIS IS", spoken once.
- Name of vessel in distress (spoken three times) and call sign or boat registration number, spoken once.
- Repeat "MAYDAY" and name of vessel, spoken once.
- Give position of vessel by latitude or longitude or by bearing (true or magnetic, state which) and distance to a well-known landmark such as a navigational aid or small island, or in any terms which will assist a responding station in locating the vessel in distress. Include any information on vessel movement such as course, speed and destination.
- Nature of distress (sinking, fire etc.).
- Kind of assistance desired.
- Number of persons onboard.
- Any other information which might facilitate rescue, such as length or tonnage of vessel, number of persons needing medical attention, color hull, cabin, masks, etc.
- The word "OVER"
You should practice copying text, including asking for repeats and phonetic spelling.
The best practice is participating in drills and public service events for your local ARES/RACES emergency communication group.
Here is a recorded VHF marine distress call. You can find more of these on YouTube.
For more information about maritime Morse, start with the Night of Nights, which runs maritime Morse one day per year on July 12.