Rule 28 explains how day shapes and lights show a vessel's navigation status

Signals that speak to you even before you hear a horn

If you’ve ever watched a busy harbor or a narrow channel squeeze a fleet of vessels into a single rhythm, you know that communication isn’t just about radio chatter or loud horns. It’s about what you can see—the shapes in the daylight and the lights at night that tell other mariners exactly how you’re moving, or what you’re able to do. Rule 28 of the COLREGs is a quiet but mighty player in that daily choreography. It lays out the display of day shapes and lights based on a vessel’s navigation status, so everyone on the water can read each other’s intentions at a glance. Let me explain why that matters, and what it looks like in practice.

What Rule 28 is really saying

Here’s the thing: within crowded waterways, guesswork is expensive. A small misread can lead to close quarters situations, where even a moment of hesitation can ripple into danger. Rule 28 acts like a shared vocabulary. It tells mariners what to display, and when, so another vessel can correctly infer what you’re doing and how you’re operating. Day shapes are used in daylight to convey a vessel’s status, and lights are used after dark for the same purpose. The rule covers a few common statuses—things like “I’m underway,” “I’m anchored,” “I’m restricted in my ability to maneuver,” or “I’m fishing”—and it provides the standardized signals tied to each of those statuses.

Think of it as the maritime version of road signs, but with a nautical twist. You don’t have to rely on a verbal back-and-forth in the glare of a busy channel; you can glance at the other boat and know whether it’s safer to pass, slow down, or hold your course. That clarity is the backbone of safer, more predictable sailing, especially when visibility is limited or when traffic is nose-to-nose in a tight approach.

What kinds of signals you’ll encounter

Rule 28 isn’t a long library of obscure markings; it’s a practical toolkit. In daylight, day shapes are displayed to show a vessel’s status; at night, corresponding lights are illuminated to perform the same signaling function. The idea is straightforward: the signal tells other mariners what you’re doing so they can plan their own actions accordingly.

To give you a clearer sense without getting lost in the weeds, here are the general categories you’ll see signals for:

• Vessel underway: Signals that indicate you’re making way through the water. Other ships know you’re moving and can factor that into their own decisions.

• Vessel anchored: Signals show you’re at rest but not drifting. This matters for approaching boats that would otherwise risk an accidental encounter if you were still or moving unpredictably.

• Vessel not under command: A clear signal that the vessel cannot maneuver as required by the rules, which prompts nearby vessels to give wide room and adjust speed.

• Vessel restricted in its ability to maneuver: This tells others that your options are limited—perhaps due to machinery, tow, or other restraints—and you need space to operate safely.

• Vessel fishing: Signals that you’re actively engaged in fishing, which has its own implications for crossing and overtaking maneuvers.

• Vessel sailing: A vessel under sail with mechanical propulsion may have a different signaling pattern; it communicates that you’re primarily powered by sails.

Why these signals matter to you (even outside the test room)

If you’re out on the water for real, Rule 28 is a practical compass. The signals aren’t just about “passing the test” or checking a box; they’re about shared safety. When you can interpret signals quickly, you can make smarter, safer choices. You’ll know when to come in closer, when to hold a little extra distance, and when you can expect another vessel to take action.

A few everyday scenarios show why this matters:

• A calm day in a busy harbor: You spot a vessel ahead with a day shape indicating it’s not under command. You slow down early, give plenty of sea room, and work with the flow of traffic rather than fighting against it. That caution pays off in calm seas and busy docks alike.

• A narrow channel at dusk: The same vessel might switch to lights at night. If you know to expect a certain lighting pattern, you can judge speed and distance more reliably, even when the water is mirror-smooth and visibility is oddly deceptive.

• Foggy lanes offshore: The signals in Rule 28 work best when combined with sound signals and radar awareness, but the visual cues give you a baseline understanding of what others are dealing with. It’s like reading the weather on a forecast map—just simpler and more immediate.

How to read the signals like a seasoned captain

Reading Rule 28 signals is a habit you can develop, almost like reading a language you use every day. Here are a few practical tips to keep in mind:

• Look for the whole picture: Day shapes tell you about the vessel’s status, while lights confirm it after dark. In poor visibility, you might rely more on lights, but in daylight, day shapes do the heavy lifting.

• Don’t assume, observe: If another vessel is signaling “restricted in its ability to maneuver,” give extra space. This isn’t about who has the right of way; it’s about preventing surprises.

• Maintain your own signaling: If you’re the one who must slow, stop, or alter course, make sure your signals are clean, visible, and current. A faded light or a partially obstructed shape isn’t just sloppy—it’s dangerous.

• Keep signals in good shape: Over time, lights burn out and day shapes fade. Regular checks are part of responsible seamanship, just like checking the oil or testing the radio.

A field guide you can remember by heart

If you’re ever tempted to overthink it, remember this: Rule 28 is the daylight-and-dark version of a good courtesy rule. It’s about making your status obvious to others so they can respond safely. You might not memorize every specific shape or every light pattern, but you’ll recognize the general idea—“I’m working with you; stand by; I may need extra space.” That awareness is what keeps the water safer for everyone.

A quick mnemonic you can carry with you:

• Day shapes: Status signals in daylight (underway, anchored, not under command, restricted in maneuver, fishing, sailing—not an exhaustive list, but a helpful mental map).

• Night lights: The same statuses echoed in light form when the sun goes down.

• The rhythm: See signal → interpret intent → adjust your actions → stay clear of danger.

What this means for real-world navigation

On the water, signals aren’t decorative; they’re functional. They help you form a quick, reliable mental model of what other vessels are doing. When everyone adheres to Rule 28, the stream of boats becomes a more predictable dance rather than a chaotic rush. You can anticipate, you can plan, and you can respond with intention.

There’s also a gentle lesson here about flexibility. The rule covers common states, but you’ll encounter unexpected situations too. A vessel signaling “not under command” might be drifting toward a critical turn, or a fisherman might appear with portable gear that changes the approach for nearby traffic. In those moments, the signals become a guide but not a guarantee. Your job is to stay vigilant, use all available information, and be ready to adapt.

A few practical thoughts for everyday sailors

• In crowded waters, slow down a notch earlier than you think you need to. Signal reading isn’t just about avoiding collisions; it’s about reducing the cognitive load for everyone nearby.

• Regularly inspect your own signals. If you notice dim lights, damaged day shapes, or anything that could obscure visibility, address it before you’re in the thick of it.

• Pair visual signals with practical sound signals when visibility is limited. A horn blast or a whistle can reinforce what you’re already seeing, reducing ambiguity.

• Learn the core categories, not just the names. When you’re under pressure, you’ll react faster if you have a mental map of what each signal implies rather than recalling a long list.

A last thought to carry offshore

Rule 28 isn’t the flashiest part of the COLREGs, but it’s the steady friend you want at the wheel in busy channels and foggy mornings. It gives every mariner a shared, readable set of cues that translates a vessel’s status into a simple, visible message. In practical terms, that message saves time, reduces risk, and keeps passage flowing smoothly for all who share the water.

If you ever find yourself glancing at a distant boat and wondering what its shapes or lights are saying, that moment of calm recognition is Rule 28 at work. It’s a reminder that navigation isn’t just about speed or skill; it’s about clear, honest signaling and mutual respect on the move.

And the next time you’re out there, take a moment to appreciate the quiet choreography around you—the day shapes catching a glint of sun, the lights beginning their quiet watch, and the way everyone on the water seems to be listening to a single, universal language. That’s the heart of safe navigation, and Rule 28 is a big part of why it all makes sense.