Around I boat, the waters are cold even in summer. You can get hypothermia in as little as 20 minutes. While we rely on phones while on land, VHF radios are the weapon of choice on the water since they broadcast the signal and many other boaters can hear it and potentially come to your rescue. There is a proper protocol for calling for help which this video from Australia nicely demonstrates. Note that channel assignments and usage can vary based on country you live in. So be sure to check for that before running with what is stated in this video.
Also for those of you in US, Digital Selective Calling or DSC has been mandatory in US radios for a few years now which provides an automated distress call. I will try to find a video showing the aspects of that system. Please watch the video. Knowing what to do will greatly reduce the stress of emergencies, enabling you to act more efficiently and reduce or eliminate the chances of injury or loss of life. Hopefully you never have to use any of this but better be prepared:
Also for those of you in US, Digital Selective Calling or DSC has been mandatory in US radios for a few years now which provides an automated distress call. I will try to find a video showing the aspects of that system. Please watch the video. Knowing what to do will greatly reduce the stress of emergencies, enabling you to act more efficiently and reduce or eliminate the chances of injury or loss of life. Hopefully you never have to use any of this but better be prepared: