So instead of saying to the coastguard - 'gulp... help - you've got to rescue me - I am sinking south of Dover' I am trained to say 'Mayday Mayday Mayday. This is Yacht PicoMicroYacht. Mayday. Yacht PicoMicroYacht. My position is 51 degrees, 4.8 minutes North, 1 degree, 19.5 minutes East. I am sinking. I require immediate assistance. There is one person on board. I have no liferaft' Of course this requires a bit of practice to do calmly and accurately when you are sinking in PicoMicroYacht.
It helps if you have made a radio call to the coastguard before setting off, telling them of your voyage and giving them a description of your boat. For PicoMicroYacht, this is an interesting conversation, short of course, because they have other things to attend to like coordinating rescues.
As well as a VHS radio, I take a mobile phone in an aqua pac, which meant it survived a capsize recently when taken sailing. Mobile phones are quick for getting in touch, but they have disadvantage that you can only speak to one person at a time, whilst the radio will broadcast to everybody. But Vodafone were good at telling me that I was in France.
I also have a Fast Find Personal Locator Beacon (PLB). The PLBs are designed to send out a satellite signal to the coastguard when you are in trouble. Mine is fitted with a GPS to provide exact location. The idea is that in trouble you pull out the whippy antenna and it transmits. I keep it on a lanyard round my neck.
The support boat used by Full Throttle Boat Charters (http://www.fullthrottleboatcharters.com/) has EchoMax, which amplifies an incoming radar signal and sends it back in a form that it is easy to spot on a screen. Radar is a good device for low visibility, but it is known that radar operators do not always monitor accurately signals from small ships. In addition, the support boat had radar and an Automatic Identification System (AIS), which picks up signals from all large vessels and plots their location, direction and speed on a map in real time. It can tell you whether a ship is on collision course or not. It also has an AIS transponder that provides an AIS signal for the support boat so other ships can see him on their map. This is a very effective way of alerting large ships to your presence.
I wear an automatically inflating life jacket, even though this impedes rowing somewhat.The life jacket is fitted with crotch straps, which can extend life expectancy in the water by about six hours in UK summer water. Surprisingly, these are not fitted routinely on lifejackets.