The Safety Network and GMDSS
The safety of people and craft at sea
First principle, Self Assistance
For everyone who ventures out on the water the first principle of rescue should be Self Assistance. Surely the people best equipped to deal with any marine emergency are those closest to it. If you fall overboard from your yacht your first line of rescue in a timely fashion is undoubtedly the very yacht that you fell off (unless you are single-handed).
Your next most likely rescuer is on another boat close to you, and great thought should be put into the best way to summon assistance from those closest to you. In the past that was always the purpose of flags, sound signals and later flares. More recently VHF radio, DSC (Digital Selective Calling), Direction finders and AIS beacons have provided ever more high-tech ways to enable the basic principle of Self Assistance.
There comes a point during any maritime distress when Self Assistance is either impossible or it is essential to inform authorities ashore of what is happening. The GMDSS system provides this crossover between Self Assistance, summoning assistance from those closest to you and informing the Authorities and summoning outside help.