When a collision risk exists, vessels must indicate their maneuvers using sound signals under COLREGs

Outline (skeleton for flow)

• Hook: When a collision risk exists, signaling isn’t optional—it's how vessels talk to stay safe.

• Core idea: In COLREGs, vessels must indicate maneuvers with sound signals to share intent.

• How sound signals work: The basics of the standardized whistle language and why it matters in fog, dusk, or busy waterways.

• Why it matters: Reducing confusion, coordinating actions, and buying time to react.

• Real-life feel: Scenarios like crossing, overtaking, and meeting head-on—how signals guide the other vessel.

• Practical guidance: Simple habits mariners can adopt; keeping the whistle handy, listening, and practicing signals with the crew.

• Wrap-up: Safety through clear communication, collaboration, and steady nerves.

When a collision risk arises, the signal is simple, but it’s pure gold in a pinch: indicate your maneuvers using sound signals. Think of it as maritime call-and-response, a way to lay your cards on the table without shouting across the water. The moment you sense danger, your signals tell other vessels what you intend to do next. That shared understanding can be the difference between a close call and a clean pass.

Let me unpack this a bit, so it lands where you live on deck, not just in theory. At sea, visual cues aren’t always reliable. Fog clings to the rigging, glare hides a silhouette, and traffic in a busy channel can make the horizon look like a moving puzzle. Sound signals cut through the awkward silence and misinterpretation. They’re not decorative; they’re functional. When two ships approach, you want to be predictable. Your signals say, “Here’s what I plan to do,” and give the other guy a chance to respond with their own plan.

What exactly do signaling rules look like in practice?

First, there’s a standardized whistle language that ships use. A vessel will emit certain sounds to indicate its intended maneuver. The signals aren’t random; they’re codified so any competent mariner can read the intent from a distance. The general idea is straightforward: use the whistle to convey your course change or speed adjustment so the other vessel understands your plan before you actually execute it. It’s a quick, nonverbal exchange that complements light signals and radio communication.

You’ll hear talk about “prolonged” vs. “short” blasts. In everyday navigation, a prolonged blast (a long, steady blast from the whistle) is a key starter, and then you follow it with short blasts as needed to refine the message. The combination of blasts is designed to say, in naval shorthand, “I’m changing course,” “I’m increasing speed,” or “I’m slowing down”—all while you’re still several boat-lengths away from a collision risk. The important thing isn't the exact words, but the clarity and timing. If the other vessel understands your intent, you’ve already reduced the chance of a violent surprise.

Here’s the practical takeaway: when there’s a risk of collision, you don’t rely on eyes and hope. You provide a clear, audible statement of your intentions. The other vessel then has the chance to respond in kind, which means you can coordinate a safe maneuver without shouting across the water or resorting to abrupt, risky actions.

Why all this matters goes beyond the math of angles and distances. It feels almost old-fashioned, in a good way. Modern navigation gear gives you radar, AIS, gps, and all kinds of clever tools. But none of that replaces the human factor—the ability to communicate quickly and unambiguously. Sound signals are the old, reliable language of the sea. They bridge the gap when visibility is poor, when engines are loud, or when radio chatter is crowded with other messages. If you’ve ever watched a busy harbor or a crowded channel, you’ve seen this in action: a quick whistle cue, a nod from the other deck, a coordinated glide of two vessels past one another.

Let’s translate this into scenarios you’ll recognize on the water.

Crossing to starboard vs. crossing to port

• When two vessels meet and neither is clear to pass, one vessel will signal its intent to alter course. The other vessel, hearing that signal, should acknowledge and respond. The goal is a mutual, predictable path that keeps both boats out of danger. It’s not magic; it’s a pattern you learn and practice.

Overtaking in a channel

• Overtaking is a test of timing and space. The leading vessel should still communicate, because the follower needs to know whether the overtaking vessel plans to pass on the starboard or port side. The whistle exchange makes the maneuver safer, preventing the overtaker from appearing out of nowhere in the other vessel’s blind spot.

Head-on approach

• In a head-on scenario, both vessels typically signal their intention to pass on a particular side and may adjust speed. The moment you detect risk, you start the signaling routine. The other side does the same, and the result is a predictable, cooperative turn away from danger.

In all of these, the thread is simple: signal early, signal clearly, and listen. The moment you lose track of either side—your own signals or the responses you hear—you’re stepping into murky waters. The best mariners treat signaling as the first line of defense.

A few practical tips that keep signaling effective in real life

• Keep the whistle clean and accessible. A whistle tucked away in a pocket or buried in a bag is useless in a hurry.

• Practice the cadence with your crew. A quick drill, even a few minutes before a voyage, makes the signals automatic under pressure.

• Don’t mix signals with other noises. If you’re racing through chop or a strong wind, you might need to emphasize the signal with a longer blast before breaking into shorter ones.

• Listen carefully. It isn’t enough to blow; you must hear what others are saying back. Keep a steady listening watch—headphones off, ears open.

• Don’t assume. If you’re unsure whether the other vessel understood your signal, repeat or adjust your message. Clarity beats speed here.

• Combine signals with other cues. A light on or a radio call can reinforce the message, but never rely on a single channel. Use sound signals as your primary, unambiguous cue.

A quick mental checklist for living by the signals

• Do I plan a maneuver, and have I signaled it?

• Am I listening for a response, and is it clear?

• If the other vessel acts unexpectedly, can I adapt quickly without creating new risk?

• Are my signals appropriate for the conditions (visibility, noise, traffic)?

• Do I have a clean, audible signal available in case of engine trouble or equipment failure?

These aren’t rigid rules carved in stone; they’re practical habits that make the sea feel safer for you and everyone around you. The goal is coordination, not choreography. You want the water to feel like a shared space where everyone understands where the other person is headed.

A note on nuance and human judgment

Sure, the code provides a framework, but real navigation is a dance of judgment. Weather, current, and vessel speed add twists that you won’t find in a textbook. The signal system is the reliable beat you can always return to. It keeps the rhythm of the encounter predictable, even when the wind picks up or the channel gets crowded. When the risk of collision exists, signaling is your best friend because it translates intention into action—fast and unambiguous.

If you’re standing on deck and the fog rolls in, or if you’re guiding a convoy through a busy harbor, you’ll notice something: those signals aren’t just about being polite. They’re about safety, predictability, and respect for the other crew who shares your space. It’s a language you learn by doing, with a little patience, a lot of listening, and a willingness to be clear even when you’d rather be quiet.

In a nutshell: when risk of collision exists, indicate your maneuvers with sound signals. It’s a simple rule with a big payoff. It keeps ships aligned in their thinking, reduces the chance of misread intentions, and gives everyone a better shot at a smooth, safe passage. That’s the essence of good seamanship—clear communication, steady hands, and a shared commitment to staying out of harm’s way.

So next time you’re at the helm, and the sea starts to tighten around you, remember this. A few deliberate sounds from the whistle can set the whole deck at ease. It’s not dramatic; it’s dependable. It’s the conversation you have with the water when you’re choosing the safest path forward. And that, more than anything, is what keeps mariners safe, sane, and moving forward together.