Emergency Communication at Sea: What You Need to Know
When something goes wrong at sea, communication is often the difference between a rescue and a tragedy. The ability to send a distress signal, convey your position, and coordinate with emergency services is not a luxury. It is one of the most critical safety systems on any vessel.
Bottom line
The short answer to what you need: a marine VHF radio as your first line of communication, and a 406 MHz emergency beacon (a PLB at minimum, a full EPIRB for offshore work) for when things get serious. Satellite communication becomes necessary as you move further offshore.
But maritime communication is not one-size-fits-all. The right tools depend on where you are boating, how far offshore you venture, and what kind of vessel you operate. This guide covers the essential devices, how to use them correctly, and what every mariner should understand before leaving the dock. It draws on what our team at Liferaft Services sees every day selling and servicing this equipment.
Understanding Emergency Communication at Sea
Modern maritime emergency communication is built around the Global Maritime Distress and Safety System (GMDSS), an internationally recognized framework established by the International Maritime Organization (IMO). It defines how vessels at sea send and receive distress alerts, safety information, and communications with rescue authorities.
GMDSS divides the world's oceans into sea areas (A1 through A4) based on radio coverage, and specifies which equipment is required for vessels operating in each area. Commercial vessels subject to SOLAS are required to carry a full complement of GMDSS equipment. Recreational mariners are not always legally required to comply, but understanding the system, and having equipment compatible with it, dramatically increases the odds that a distress call reaches the right people in time.
The core principle behind GMDSS is that no single device is enough. Layering multiple communication tools ensures that if one fails, another is available. That redundancy is what saves lives.
Why Your Cell Phone Is Not Enough
One of the most common misunderstandings we hear is that a cell phone is good enough. It is not. Cell coverage typically ends within a few miles of shore, battery life is limited, and phones are not built to survive the conditions of a real emergency at sea. A phone is a useful extra, never a substitute for dedicated emergency equipment.
Essential Emergency Communication Devices
Here is a breakdown of the primary tools every mariner should know, with specific product examples representing the standard in each category.
Marine VHF Radios
The VHF marine radio is the backbone of short-range maritime communication and your first line for help. Channel 16 is the international distress and calling frequency, monitored by the Coast Guard, commercial vessels, and recreational boaters alike. A VHF radio is the first tool you reach for in a near-shore emergency and an essential means of hailing nearby vessels.
When selecting a fixed-mount VHF, look for Digital Selective Calling (DSC) capability. DSC allows you to send a digital distress signal with your vessel's MMSI number and GPS position at the press of a button, automatically alerting the Coast Guard and any nearby vessels without the need to speak. The Standard Horizon GX1400 Eclipse is a reliable DSC-capable radio with 25W power output and NOAA weather alerts (the GX1400GPS version adds a built-in GPS). It is an appropriate choice for coastal and inland cruising vessels of any size.
A handheld VHF is the essential backup. It keeps working if your vessel loses power, and it goes with you if you have to abandon ship. Look for a waterproof, floating model, ideally with DSC and GPS. Radios such as the Icom IC-M94D add AIS as well. A handheld VHF belongs in every ditch bag, so you can talk to rescuers and nearby vessels from the liferaft.
EPIRBs (Emergency Position-Indicating Radio Beacons)
If there is one category to get right, it is this one. Other than a good life jacket, an emergency beacon is the number one piece of safety equipment everyone should have onboard, even before a liferaft. And unlike satellite phones and messengers, EPIRBs and PLBs have no subscription fees or ongoing costs other than periodic battery replacement.
An EPIRB is a dedicated distress beacon that, once activated, transmits a 406 MHz signal to the COSPAS-SARSAT satellite network, a system maintained specifically for maritime and aviation rescue. The signal is relayed to rescue coordination centers, who use it to initiate a search and rescue response. Modern EPIRBs with integrated GPS can transmit your precise location within minutes of activation, and they are built to transmit for at least 48 hours.
EPIRBs come in two mounting categories. A Category I EPIRB sits in a bracket with a hydrostatic release, so if the vessel sinks it floats free and activates automatically. A Category II EPIRB mounts in a manual bracket and is activated by hand or when removed from its bracket and placed in the water. Certain commercial vessels are required to carry Category I units, while recreational boaters can choose either.
The ACR GlobalFix V6 is our standard recommendation. It uses GPS, Galileo, and GLONASS positioning to locate you within 100 meters, and its Return Link Service flashes a blue light to confirm your distress signal has been received, which is real reassurance in an emergency. It also connects to ACR's free app over NFC so you can check battery life and self-test history from your phone.
For an added layer of protection, the ACR GlobalFix V5 AIS adds a built-in AIS transmitter. In addition to the 406 MHz satellite alert, it broadcasts your position directly to AIS-equipped vessels within VHF range, where it appears as a target on their chartplotters. That means boats nearby can see you and start heading your way without waiting for rescue authorities to relay the alert. For a deeper look at the differences, see our guide to emergency beacons.
PLBs (Personal Locator Beacons)
A PLB works on the same 406 MHz satellite system as an EPIRB, but it is smaller and designed to be carried on your person, clipped to a life jacket or kept in a pocket. Because it stays with you rather than the boat, a PLB protects you if you go overboard or have to leave the vessel in a hurry. PLBs are activated manually and transmit for at least 24 hours. Like EPIRBs, they carry no subscription fees, and they should be registered with NOAA so rescuers can reach your emergency contacts.
ACR's ResQLink line is the most popular choice, from the compact ResQLink 410 RLS with Return Link Service to the ResQLink AIS, which adds an AIS alert to nearby vessels.
A PLB's value is easy to underestimate until you hear how it plays out. Our team recently spoke with a NOAA fisheries observer who always carries a PLB in the field. While she was aboard a commercial fishing vessel, the boat began to sink, so quickly that the captain and crew were unable to activate their own EPIRB or make a distress call before they had to abandon ship to their liferaft. Following her training, she activated her PLB, which alerted the U.S. Coast Guard and brought help to their location. She credits their survival to the beacon she had with her that day.
Satellite Messengers & Trackers
Satellite messengers fill an important role between a VHF radio and a full satellite phone. They provide two-way text messaging, GPS-based tracking, and, most critically, an SOS function that transmits your position to a search and rescue coordination center even if you cannot speak.
The Garmin inReach Mini 2 packs those capabilities into a device small enough to clip to a life jacket. Its SOS function connects to Garmin's 24/7 International Emergency Response Coordination Center, which coordinates with local rescue authorities, and you can trade text messages with responders so they know what is happening. For sailors, offshore racers, and cruisers who want reliable tracking and two-way communication without the cost of a satellite phone, the inReach is a practical and proven choice. Note that, unlike an EPIRB or PLB, it requires an active satellite subscription.
Satellite Phones
When cellular coverage ends, which happens within a few miles offshore in most areas, satellite phones become your primary voice communication link. They operate through dedicated satellite networks that provide near-global coverage regardless of how far you are from land.
The Iridium Extreme 9575 is widely regarded as the gold standard for offshore use. It operates on the Iridium satellite constellation, which provides true pole-to-pole global coverage, including high-latitude routes where other networks have gaps. It is ruggedized for marine environments, offers an integrated GPS, and has an emergency SOS function that connects directly to a 24/7 response center.
The Inmarsat IsatPhone 2 is a strong alternative for vessels operating in mid-latitude zones. It delivers excellent voice clarity, long battery life, and a durable build suitable for offshore conditions. Coverage does not extend to the poles, but for the majority of ocean passages it provides reliable performance at a competitive cost.
SARTs (Search and Rescue Transponders)
A SART is a radar transponder designed to make a liferaft, survival craft, or person in the water visible on the radar screens of nearby vessels and aircraft. When interrogated by an X-band (9 GHz) radar, it responds with a distinctive line of dots on the radar screen that pinpoints its location. SARTs are particularly valuable in poor visibility, where visual searches are limited.
The ACR Pathfinder Pro SART is a compact and reliable option that complies with IMO SOLAS requirements and is suitable for both commercial and offshore recreational vessels. It floats, comes with a telescoping pole to raise it above the waves for better radar detection, and offers more than 96 hours of standby time and more than 12 hours of active transmission.
Distress Communication Protocols
Knowing which call to make, and how to make it, is as important as having the equipment to make it with. Sending a distress call is actually very simple, but most boaters have never practiced one and would not know what to do if they had to make one today. There are three levels of maritime radio urgency:
MAYDAY
Reserved for situations involving grave and imminent danger to life or vessel. Broadcast on VHF Channel 16 using the format: "Mayday, Mayday, Mayday," followed by vessel name and MMSI, position, nature of distress, number of persons aboard, and any other relevant information. If no response is received, repeat the call.
PAN-PAN
Used for urgent situations that require assistance but do not involve an immediate threat to life, such as a medical emergency, a vessel taking on water slowly, or a disabled vessel in a shipping lane. Same broadcast format as Mayday, with "Pan-Pan" repeated three times in place of "Mayday."
SECURITE
A safety call used to broadcast navigational hazards or weather warnings to other vessels. It is not a distress call. Pronounced "say-cure-ee-tay." Common uses include alerting nearby traffic to a floating hazard or announcing a vessel's departure from a harbor into a shipping lane.
All three calls are broadcast on VHF Channel 16 unless DSC is being used, in which case the initial digital alert is sent first and followed up with voice communication on Channel 16.
Choosing the Right Communication Equipment
No single device covers every scenario, but there is a clear baseline. A VHF radio should already be on every boat. Beyond that, there is no excuse not to carry at least a PLB, and a full-size EPIRB is even better. If you can afford a boat, you should not be leaving the dock without a beacon.
From there, the right communications suite depends on three primary factors:
- Voyage distance: Coastal boaters are well served by a VHF radio plus a PLB, which transmits for a minimum of 24 hours when activated. Offshore voyages warrant a full EPIRB with at least 48 hours of transmission time, and beyond 20 to 30 miles you should add satellite communication, such as an inReach or a satellite phone.
- Vessel type: Commercial and SOLAS-compliant vessels have defined equipment requirements by sea area. Recreational vessels must assess their own risk and coverage needs independently.
- Crew size and experience: Shorthanded crews and single-handed sailors face greater risk when incapacitated. Devices with automatic or one-touch SOS, like a Category I EPIRB or a PLB worn on your life jacket, provide a safety net that does not depend on reaching the helm.
Fixed VHF radios aboard U.S. vessels traveling to foreign ports require an FCC ship station license. Make sure any DSC-capable radio is programmed with an MMSI number. Without it, the automatic distress alert cannot identify your vessel.
Maintenance & Training
Equipment that has not been tested is equipment you cannot rely on. The most common failures we see are old EPIRBs and PLBs with expired batteries, units that are failing self-test, and equipment that simply has not been looked at in years.
It happens more than you might think. Boat owners often remember having "just bought" a piece of equipment a year or two ago. In reality, it is ten years old and has not worked for the last five because the battery is dead or the unit is damaged.
Before each voyage, run through a basic check:
- ✓Power on and confirm operation of your VHF radio, satellite messenger, and any handheld backups.
- ✓Self-test your EPIRB and PLB, and check their battery expiration dates and the condition of any hydrostatic release. EPIRBs are designed with enough battery capacity to allow monthly self-testing over the life of the unit. One of the biggest mistakes we see is people not knowing their EPIRB has a problem because they have never self-tested it. Many are nervous about setting it off by accident, so they leave it on the boat for five or ten years until the battery expires. If you discover early that your EPIRB or PLB is failing self-test, you have a better chance of replacing it under warranty and, more importantly, of having a working unit when you need it. When the battery is near expiration, send it in for EPIRB and PLB battery replacement.
- ✓Confirm your satellite phone or messenger service plan is active and the unit can acquire a signal with a clear view of the sky.
- ✓Test DSC on your VHF by sending a DSC test call (not a false distress alert).
Don't be afraid of your safety equipment. Accidentally setting off your EPIRB and getting a call from the Coast Guard might be embarrassing, but unknowingly carrying a non-working EPIRB for five years and having it fail in an emergency is far worse.
Training matters just as much as the equipment itself. Just like a fire drill at school, you do not want the first time you run through an emergency to be the real thing. Every crew member who might need to operate communication equipment in an emergency should practice doing so. Running a Mayday drill, locating the EPIRB, and knowing how to trigger an inReach SOS are skills that fade quickly without practice. Add a brief communication review to your pre-departure safety briefing.
Communication Is Your Link to Safety
Every device covered in this guide exists for the same reason: to make sure that if something goes wrong, help can find you. The best emergency communication plan is layered, tested, and understood by everyone aboard.
Assess your typical voyages, confirm what regulatory requirements apply to your vessel, and build out your communications suite accordingly. Then test it, train on it, and brief your crew. When the situation is calm is exactly the right time to prepare for when it is not.
Survival at Sea sells and services all major emergency communication devices, including EPIRBs, PLBs, and SARTs. ACR is our preferred brand for safety communication devices. If you are not sure what your boat needs, or whether your current beacon is still working, shop emergency beacons or give our team a call at (207) 363-0220.
Frequently Asked Questions
What is the most important emergency communication device on a boat?
A 406 MHz emergency beacon. After a good life jacket, an EPIRB or PLB is the most important piece of safety equipment you can carry, even ahead of a liferaft. It works anywhere in the world via satellite, has a long-lasting battery, and requires no subscription. A VHF radio should already be aboard as your first line for help.
What is the difference between an EPIRB and a PLB?
Both send a 406 MHz distress signal through the COSPAS-SARSAT satellite system. An EPIRB is registered to the vessel, has a larger battery that transmits for at least 48 hours, and can activate automatically. A PLB is registered to a person, is small enough to wear on a life jacket, must be activated manually, and transmits for at least 24 hours.
Do I need an EPIRB for coastal boating?
Coastal boaters are generally well covered by a VHF radio plus a PLB. Offshore boating warrants a full EPIRB with at least 48 hours of transmission time, plus satellite communication such as an inReach or satellite phone.
Do EPIRBs and PLBs require a subscription?
No. EPIRBs and PLBs have no subscription or monthly fees. The only ongoing cost is battery replacement at the end of the battery's rated life. Satellite messengers and satellite phones, by contrast, require an active service plan.
How often should I test my EPIRB?
Monthly. EPIRBs are designed with enough battery capacity to self-test once a month over the life of the unit. Regular self-testing catches problems early, while the unit may still be under warranty, rather than in an emergency.
Can I rely on my cell phone offshore?
No. Cell coverage usually ends within a few miles of shore, and phone batteries are not built for extended emergencies. Carry a VHF radio and a 406 MHz beacon, and treat your phone as a backup only.