Most parts of the World are monitored by national coastguards. This means that if you get into trouble within a few miles of the coast and you have a VHF radio, you are able to call for help, confident that someone will be listening. Of course, if you are further offshore, you may need to rely upon other seafarers in your immediate vicinity. This is why we are all obliged to maintain a radio watch when at sea.
The most well known radio call is the Mayday. Internationally recognised as a distress call, the mayday call should only be sent when the person in charge of the vessel considers that the vessel or its crew are in imminent and serious danger of loss of life or vessel. A man overboard or significant water ingress (in other words, you are sinking) would be examples of situations where a mayday call might be transmitted. Modern DSC VHF radios now have a red button with a cover over it. Pressing this for 5 seconds will automatically open a menu allowing you to send a VHF Distress Call without the need to use a voice call. Check your VHF set’s user manual or with your skipper on how to use this function.
In other situations, you may have a problem but it is not immediately life threatening. Perhaps you have fouled a lobster pot and can’t get off, or you have lost your engine and cannot make sufficient way under sail alone. In such cases the skipper may consider issuing a Pan Pan call. This tells the world around you that the call is urgent. You have a problem and would like some assistance but it is not a life threatening event.
Given the demands upon coastguards around the world, it’s worth knowing the difference. You are unlikely to be thanked if you issue a mayday call when you have simply hooked a lobster pot on a calm and sunny Saturday morning in July when the emergency services have a man overboard recovery underway elsewhere. That said, should your problems get worse and your initial Pan Pan now seems more serious (perhaps you are now on a lee shore with the weather deteriorating and the sea state has built. You know it is likely to get dark in a couple of hours and the forecast is for a gale to blow in overnight). At that point what was a pan pan might quickly escalate to a Mayday. If that happens, then make it clear you are calling a Mayday.
If you do not have a VHF radio then consider using red flares or switching on your EPIRB (if you have one) to send a distress message. Alternatively, mobile phones sometimes work several miles offshore. Dial 999 and ask for the coastguard.