Rule 23 Emergency Signals: How vessels signal emergencies and why it matters on the water

Rule 23 and the signals that speak for the sea

When you’re out on the water, you can’t help but notice the fog of nerves and the bustle of traffic—the hum of engines, the flashing navigation lights, the occasional flare slicing through dusk. In the middle of all that, Rule 23 does something simple and important: it tells us how a vessel should behave when it’s signaling an emergency. Not how others should react, not what to do in a collision risk. It’s about the signaling itself—the language of distress that other ships are supposed to understand.

What Rule 23 actually says

Let me explain the gist. Rule 23 is the rule that covers distress signals. It sets out that a vessel in distress, or one needing urgent assistance, must use signals that are widely recognized as indicating distress or an emergency. Think of it as the international code that turns a scary moment into a clear message: “Hey, I’m in trouble, please help.” The emphasis is on the behavior of the signaling vessel—the way they communicate, the signals they deploy, the timing, and the escalation if one signal isn’t enough.

This isn’t about memorizing a list of arbitrary actions. It’s about reliable communication. The signals themselves can be visual, audible, or electronic, but they all share a common goal: to be unmistakable to nearby vessels and rescue services. And because water is a global commons, these signals aren’t arbitrary to one coast or country—they’re recognized far and wide, from the busy channels of the North Sea to the marshy estuaries of the delta.

A quick tour of the kinds of signals you might encounter

• Visual signals: Flares, orange or red smoke, and other pyrotechnic devices are classic distress signals. A common example is a red parachute flare or a hand-held red flare. These have a long track record for grabbing attention in daylight or night conditions.

• Sound signals: In calm seas, a prolonged or repeated distress signal might be heard as a warning to nearby traffic that someone needs help. The exact patterns vary by system, but the idea is the same: the sound calls for attention and help.

• Radio signals: The phrase “Mayday” spoken over VHF Channel 16 (or 2182 kHz on HF) is the digital heartbeat of a distress call. Modern kits can also integrate digital safety channels and emergency position-indicating systems.

• Electronic beacons and devices: EPIRBs and AIS-SARTs are designed to trigger a rescue response automatically when immersed in water or when a distress signal is activated. These tools are part of the modern signaling toolkit and are intended to speed up the location of people in need.

Why signaling behavior matters in the real world

Here’s the thing: signaling is not a solo act. When a vessel signals distress, nearby boats have a responsibility to recognize and interpret the message correctly. The rules aren’t just about what you should do if you see a flare; they’re about what you should expect another vessel to do when it’s signaling trouble. Clear signaling reduces ambiguity, buys time, and increases the odds that help arrives quickly and safely.

If a vessel signaling distress doesn’t use recognized signals—if someone shouts “help” but doesn’t deploy the standard flare at the right moment, or if a radio distress call never gets onto the correct channel—confusion follows. In those moments, hesitation can cost precious minutes. Rule 23’s strength lies in reducing that hesitation by offering a universal, recognizable language for distress.

Distinguishing Rule 23 from related ideas

You might be wondering, “If Rule 23 is about signaling, what about the other bits I’ve heard—like how to react to an emergency signal, or what to do when you encounter distress signals?” That’s a fair question, and it’s a good one to keep in mind as you study.

• Specific actions in collision risks (not Rule 23): These are the rules that guide how vessels should maneuver to avoid a crash. They focus on decision-making in the moment of risk, not on signaling.

• How vessels should react to an emergency signal (response, not signaling): This is about the behavior of other vessels once a distress signal is seen. It’s crucial for safety, but it’s a step downstream from the signaling act itself.

• Safety measures when encountering distress signals (procedural response): This covers procedures for responders—what to do when you find someone distress signals, how to render assistance, and how to coordinate with rescue services.

Rule 23 shines a light on the signaling side of things. It’s about the message you send and how you make sure it’s heard and understood. Once that message is out there, the rest of the ecosystem—watchkeeping, traffic separation schemes, and the cooperative safety rules—kicks in to guide the response.

What signaling behavior looks like in practice

• Clarity over cleverness: The goal is to be unmistakable, not flashy. A calm, deliberate use of a recognized distress signal beats clever improvisation any day.

• Timely escalation: If the first signal doesn’t get the message across, you escalate. In real life that might mean adding booms in radio calls, or firing additional flares to increase visibility. The point is to remove doubt.

• Compliance with international standards: Since the sea is international, these signals are standardized. Off-the-shelf devices that emit recognized distress signals are preferable to improvised methods.

• Documentation and preparedness: Vessels stocked with the right signaling gear, and crews trained to use it, reduce confusion when things get tense. A well-maintained EPIRB, a working VHF radio with the emergency channel, and flares that aren’t expired all matter.

A practical, no-nonsense takeaway for mariners

• Know your signals: Familiarize yourself with the most common distress signals—visual, audible, and radio-based. Practice recognizing them so you can respond instinctively when you hear or see them.

• Keep the channels open: Channel 16 on VHF and the appropriate emergency frequencies should be monitored. If you’re in distress, make your Mayday call clearly and repeatedly until you’re understood.

• Maintain your devices: EPIRBs, AIS-SARTs, and other signaling gear should be checked and tested according to the manufacturer’s guidance. Batteries age, seals wear—don’t wait until a voyage to discover a dead beacon.

• Be ready to help, but stay safe: If you’re in a position to help, do so using trained procedures and established safety protocols. If you’re not certain, coordinate with rescue services and follow their guidance.

A few analogies to anchor the concept

• Think of distress signaling like turning on a bright warning light in fog. The fog is the danger; the light is your message to others: “I need assistance, and I’m visible.”

• Picture a crowded harbor at dusk. If every boat uses the same color flag to signal distress, it’s easy to spot who needs help. If someone uses a random symbol, others might miss it entirely. Rule 23 is the standardized flag system for the open water.

Common misconceptions worth squaring away

• It’s not about “calling for help” in a generic sense. It’s about specific, widely recognized signals that others are trained to recognize.

• It’s not only about the signal itself. It’s about the entire signaling behavior—the timing, the method, and how it’s maintained until help arrives.

• It’s not restricted to one kind of vessel. Small boats, large ships, and rescue craft all rely on the same fundamental signals to communicate distress.

Putting it all together

Rule 23 is a practical bit of maritime wisdom. It does not demand drama. It demands reliability: when a vessel needs help, it communicates in a way that others can understand immediately. The safety of everyone on the water depends on that clarity—the difference between a swift rescue and a longer, riskier ordeal.

If you’re mapping out your own mental toolkit for safe navigation, add Rule 23 to the top of your signaling gear. Know the signals, understand how they’re interpreted, and practice recognizing them in different environments—day, night, calm seas, rough weather. The sea doesn’t wait for anyone, and good signaling doesn’t, either.

A quick closing thought

The beauty of the COLREGs is that they’re built to be practical, not poetic. They’re about real-life moments when the stakes are high, and timing matters. Rule 23 sits at the heart of those moments, ensuring that the language of distress—whether spoken aloud over a radio, shown with a flare, or emitted by an electronic beacon—is heard and understood. That shared understanding is what keeps mariners safer, helps rescuers do their jobs faster, and preserves the quiet confidence that, when trouble comes, the water’s communication will cut through the noise.

If you want a deeper dive, look into the basics of distress signals as described in international conventions, and check out resources from the national coast guards and search-and-rescue organizations. They’re not there to complicate things; they’re there to remind us that in the middle of the ocean, clear signals are a lifeline.