EPIRB, PLB or AIS MOB: Which Life-Jacket Device Should You Carry?

Almost every week I’m asked the same practical question: if you could carry only one device in your life jacket, would you choose an EPIRB/PLB or an AIS MOB? It’s a fair question—often raised by boaters who spend time near other vessels or in coastal waters where nearby boats might notice an AIS distress signal more quickly than a satellite alert.

Before answering, it helps to understand the key operational differences. An AIS MOB transmitter broadcasts locally to nearby ships and shore stations that have AIS receivers switched on and within range. A PLB or personal EPIRB, by contrast, transmits a distress signal picked up by global search-and-rescue satellites and relayed to monitoring centers that can coordinate an immediate rescue response.

An AIS MOB device may alert the vessel you fell from and other close boats—if those boats have their AIS receiver on and are nearby. That local broadcast can be extremely helpful in crowded or coastal areas. But AIS MOB is conditional: it relies on others being able and willing to receive and respond.

A PLB or EPIRB operates on a different principle: when it activates, international satellite networks and dedicated rescue authorities are alerted. Those monitoring centers are actively waiting for distress transmissions and can task search-and-rescue units based on the device’s transmitted position. In short, with an AIS MOB you might be noticed; with an EPIRB/PLB you will be picked up by the global system designed specifically for maritime emergencies.

That reliability is why, if forced to choose a single device to carry in my life jacket, I would pick an EPIRB/PLB. It provides a direct link to professional rescue coordination even when no other boats are within VHF or AIS range. If you keep your registration information up to date, authorities can contact your emergency contacts and dispatch help quickly.

There is growing interest in combined devices that pair AIS MOB capability with an EPIRB/PLB. Manufacturers have shown prototypes and hybrid units, but widespread, life-jacket–sized combinations have been slow to reach the market. When battery and antenna technology continues to improve, a compact, fully integrated EPIRB/AIS MOB solution will likely become common—but until then, the proven global reach of EPIRB/PLB matters most for solo personal safety.

Another common comparison is between EPIRBs/PLBs and consumer satellite trackers such as Spot or InReach-style units. Satellite trackers are excellent for sharing position, sending check-ins, and communicating with friends and family. They offer convenience and useful non-emergency features, and many boaters carry one for peace of mind. However, these devices are designed primarily for tracking and messaging; their “SOS” functions generally route through commercial relay services rather than the maritime search-and-rescue system built around beacon standards.

Because consumer trackers often have shorter antennas and are not always optimized for the harsh conditions of open-ocean signaling, they may be less reliable in a severe maritime emergency than a dedicated EPIRB/PLB. Use a satellite tracker as a complementary device: great for trip sharing, routine check-ins, and non-life-threatening situations, but not as a substitute for a certified distress beacon when lives are at stake.

To summarize practical recommendations for boaters and paddlers:

• Prioritize a certified EPIRB or PLB in your life jacket for the most reliable, internationally supported distress signaling.
• Carry an AIS MOB device if you operate frequently near other vessels and want the best chance of immediate local pickup.
• Use satellite trackers for routine position sharing and communication with family and friends, not as your primary emergency distress signal.
• If possible, carry more than one system—an EPIRB/PLB for global rescue notification, an AIS MOB for local alerting, and a satellite tracker for check-ins and messaging.

Ultimately, there’s no reason to limit yourself to a single device if you regularly go to sea. Combining technologies gives you the broadest coverage: global rescue notification from an EPIRB/PLB, local awareness from AIS MOB, and convenient communication from a satellite tracker. If you must pick only one, choose the device that will get professional rescuers started—the EPIRB or PLB.