Understanding why non-power-driven vessels use one long blast followed by two short blasts under COLREGs

What sound signal should be used by every vessel that isn’t power-driven? A quick, “got it” moment for anyone navigating in sight of other traffic.

Let me set the scene. On the water, you don’t have the luxury of bright lights like a streetlamp—nor the instant, laser-focused communication you get from a phone screen. You rely on signals that cut through wind, spray, and the ever-present murmur of waves. That’s where the COLREGs come in, the etiquette and rules that keep boats from bumping into one another. Among them, Rule 35 deals with sound signals in restricted visibility. And here’s the line that matters for not-power-driven vessels (think sailing boats, fishing boats, or anything that isn’t pushing a propeller): one long blast followed by two short blasts.

One long, two short. It sounds almost musical, doesn’t it? But it’s not a tune you whistle for fun; it’s a clear, audible cue that a vessel not under power is maneuvering or is about to make a move. In hazy or foggy conditions, where a visual signal might be lost in the gusts, that audible rhythm can be the difference between a safe pass and a close quarters collision.

Who has to use it, anyway?

Not power-driven vessels include sailing vessels and other craft that don’t rely on their engines for forward motion. They still share the water with bigger boats, ferries, fishing trawlers, and cargo ships. Even if your boat isn’t roaring through the water, you’re still responsible for communicating your intentions to nearby traffic. Think of it as a courtesy, plus a safety protocol, wrapped in a short blast sequence. The signal isn’t just a personal message to a single vessel; it’s a way to broadcast your status to everyone around you who might be affected by your next move.

What exactly does that signal communicate?

The essence is simple: a single long blast followed by two short blasts tells other mariners that you’re engaged in a maneuver or that you’re about to be. It’s not a random noise; it’s a standardized call that others can recognize quickly, even if visibility is poor. The long blast acts like a beacon, drawing attention. The two shorter blasts add specificity, hinting at an intention rather than a random drift. In practice, that means nearby boats know to expect a change in course, speed, or both, and they should adjust their own actions accordingly.

It’s helpful to picture it this way: the ocean is a crowded street at dusk. Cars (or vessels) aren’t always able to stop on a dime, and pedestrians (that’s you, the other vessel) can’t always see everything at once. Sound signals slice through the ambiguity. They’re a shared language that reduces the guesswork and keeps everyone safer.

Why is this signal particularly important for non-powered vessels?

• Visibility challenges: In fog, rain, or twilight, your engine noise might be drowned out, and lights can be harder to pick up at a distance. A distinct blast pattern can be heard well before you’re seen.

• Equal footing: Even though one vessel isn’t moving under its own power, it still has a responsibility to communicate. The signal helps fishing boats, sailboats, and other slow movers avoid misunderstandings with motor vessels that have different acceleration, stopping distances, and turning radii.

• Predictability: When a nearby vessel anticipates a maneuver, it can adjust speed or course early. That head start minimizes the risk of an abrupt, dangerous maneuver that could escalate into a near-m miss.

A few practical notes to keep in mind

• The signal isn’t a magical guarantee of safety. It’s a cue in a set of rules designed to reduce risk. Always look for other signals as well—lights, shapes, AIS, and radio communications when they’re available.

• Context matters. The same signal might coincide with other actions, like a radio call or a visible change in bearing. Use your judgment and keep scanning the water around you.

• It’s not just for emergencies. You’ll hear this sequence not only in bad weather but whenever a sailing vessel or other non-powered craft plans a turn, a course change, or a planned slow maneuver in traffic.

A little mental model to help memorize

If you ever forget the rhythm, think of it as a phrase: “Long talk, two short whispers.” The long part grabs attention; the two short bits clarify that a specific maneuver is in play. Some mariners remember it with the mnemonic “L-S-S,” where L stands for long, and S for short. It’s not a perfect summary of every possible situation, but it helps you recall the core signal quickly in the moment.

Real-life scenarios where this comes into play

• A sailing yacht preparing to tack across a channel with motor traffic nearby. The skipper might sound one long blast and two short blasts to signal the intent to change course toward the windward side while other vessels evaluate their own paths.

• A small fishing vessel slowly edging toward a fairway that’s busy with commercial ships. The crew uses the signal to indicate a calculated maneuver rather than a sudden, surprising turn.

• A sailboat halting a drift near a restricted area. The signal helps alert passing vessels to the fact that the sailing craft isn’t simply idle; it’s actively maneuvering in response to currents, wind shifts, or lines in the water.

What should the other vessels do in response?

• Keep a lookout. Don’t rely on one cue; combine it with AIS, radar if you’ve got it, and your own visual scan.

• Decide early whether you can safely pass or whether you need to slow down and wait for the non-powered vessel to complete its maneuver.

• Maintain a safe distance. If you’re unsure about the other vessel’s path, give them more room rather than pressing your luck.

• Communicate if needed. If there’s ambiguity, a brief VHF call or a radio check can clear things up and prevent tension on the water.

A few notes on how this fits with modern boating

Technology isn’t going away. AIS displays, radar, and VHF radios give you extra layers of situational awareness. The sound signal is still a critical, guaranteed line of communication when visibility smears the picture. The two systems—human-readable sound signals and machine-readable electronic signals—work best together. When in doubt, trust your ears and your eyes in tandem.

Keeping things safe, not strenuous

Here’s the takeaway: not-power-driven vessels use a standard one long blast followed by two short blasts to indicate a maneuver or intent, especially in restricted visibility. It’s a compact, universal cue designed to cut through confusion and keep traffic flowing safely. If you’re on a sailing vessel, a fishing boat, or any other non-powered craft, this little blast sequence is a powerful tool. It’s like waving a flag that says, “I’m about to turn,” or “I’m adjusting my course—watch out.”

A quick recap, in plain language

• Who uses it? Vessels not powered by a motor, such as sailing boats and some fishing craft.

• What’s the signal? One long blast followed by two short blasts.

• Why use it? To communicate an intended maneuver clearly to nearby traffic, helping prevent collisions when visibility is limited.

• How should others respond? Stay alert, assess your own path, and give extra space if needed.

A final thought, with a touch of humanity

The sea humbles us in a dozen little ways—wind shifts, stubborn currents, a horizon that seems to move as you move. In that space, a simple sound becomes a lifeline. It’s not about memorizing a rule so you can parrot it back on an exam; it’s about taking care of your fellow mariners. It’s about paying attention, listening actively, and treating every blast as a mindful invitation to share the water safely.

If you ever find yourself practicing these signals in a calm harbor or a quiet bay, take a moment to notice how easily the sound cuts through the murk. That clarity isn’t magic; it’s centuries of maritime wisdom distilled into a short sequence that keeps people afloat and carpools of boats moving without incident.

So next time you hear one long blast with two short blasts, you’ll know what it means, you’ll recognize the responsibility behind it, and you’ll be part of a shared standard that helps the water stay a safe, navigable space for everyone. The rhythm isn’t just noise—it’s a promise: I’m maneuvering, and I want you to know what I’m up to, so we can all steer clear of trouble together.