An Emergency Position-Indicating Radio Beacon, or EPIRB, is a small, battery-powered radio transmitter that sends out a signal when activated via satellite to notify emergency services the whereabouts of the vessel in distress. EPIRBs are imperative for boaters who travel long distances in large bodies of water, and are important safety devices when all other forms of communication fail. Not all boats have an EPIRB equipped upon purchase, so this should be among your first five buys before getting underway.
There are two categories. The first is the most accurate and its signals are coded, allowing non-EPIRB transmissions to be filtered out and essentially just provides more information to the rescue team who will be coming to your aid. This one will activate on its own, has a built-in GPS and is recommended by all maritime agencies as the safest of EPIRB purchases.
The second and the lower priced of the two items, alerts nearby aircraft of a seafaring incident. However, the second category is sometimes incompatible with satellites, and is manually activated.
There is an enormous difference between EPIRBs and PLBs, where the latter is designed more for climbing, gliding and other outdoor activities. A PLB can fit in your pocket, but they typically do not float and have a much shorter battery life than the EPIRB. There many boaters who preach that the EPIRB and PLB are one in the same, so be cautious: they are not.
EPIRBs are generally always bright yellow or orange plastic, are waterproof, and are designed to float upright in the water. They will transmit your SOS for up to 48 hours time. These have been the saving grace in many boating incidents and have prevented many catastrophes at sea. The number of boaters who carry these devices increases daily as people recognize the service they provide.