You Should Alter Course When Signaling Under COLREGs: Why It Beats Changing Speed

Outline

• Hook: The sea as a shared conversation—rules are the grammar; your turns are the punctuation.

• Core idea: The rule in practice — alter course when it makes the change more obvious to other vessels, not just adjust speed.

• Why visibility matters: Clear signaling reduces misinterpretation and keeps crossings safe.

• When speed changes aren’t enough: Poor visibility, big ships, or fast-moving boats make speed tweaks easy to miss.

• How to execute a clear maneuver: Lookout, assess, pick a visible course change, and tell others with signals and lights if applicable.

• Common misconceptions: It’s tempting to think slowing down alone works, but that can leave others guessing.

• Real-world analogies and tools: Radar, AIS, and the everyday “traffic” mindset at sea.

• Takeaways: Simple rules, big safety gains.

• Closing thought: Navigating is a dance of clarity—make your intentions obvious.

Why Alter Course Beats Speed When Clarity Is Key

Let me explain it this way: on the water, we’re all trying to read each other’s minds before things get messy. The COLREGs are the shared language for that read. A vessel that changes course in clear, noticeable ways sends a powerful signal to nearby boats. It’s like flashing a big arrow: “I’m turning left, watch out.” When you only slow down or speed up, you’re removing speed as a signal, but you’re not giving others a clear picture of your intent. And in busy shipping lanes or narrow channels, a vague intention can lead to misjudgments. So, the rule of thumb is simple—altering course is preferable when it makes the change more obvious to other vessels.

Here’s the thing: visibility isn’t just about daylight or clear weather. It’s about how well your actions read to others who are also watching. A sharp, noticeable course change stands out more than a subtle reduction or acceleration. It’s like driving with your turn signals on. You could slow down a bit, but if you don’t advertise your plan with a clear turn, other mariners may overreact or underreact. A visible maneuver minimizes that risk.

The truth is, there are times when a speed change can help, but those times are narrower. If you’re in a crowded harbor, in fog, or maneuvering near large vessels, simply adjusting speed may not travel far enough to communicate your intent. In those moments, a deliberate course change acts as a clearer message to others about your path ahead. Think of it as clarity over quietness—the goal is to be understood at first glance, not after a second or two of calculation.

A Few Scenarios Where Making a Visible Turn Wins

• Poor visibility: When the spray and fog smear the horizon, your radar becomes your best friend, but human eyes still crave obvious cues. A clear course change is harder to misread than a speed shift, which can be harder to detect without a full view of speed relative to distance. The idea is to minimize ambiguity in your maneuver, so others can react promptly.

• Crowded channels: In busy waterways, multiple vessels share the same space, and everyone’s got a different reaction time. A conspicuous turn helps align everyone’s mental map. It’s easier to predict a vessel that tells you, with a strong turn, where it’s headed than one that relies on speed alone to signal intention.

• Large vessels: Big ships take longer to alter momentum and longer to bring a new heading into clear view for others. If you’re a smaller boat and you see a large, lumbering vessel, making a noticeable course change can be the safer, more easily interpreted option for everyone nearby.

• High-speed craft: When you’re moving fast, your path can change quickly. A visible course alteration gives others a chance to gauge your new direction in time to adjust. Speed changes can be less obvious at a quick glance, especially if radar returns or lookouts are busy with other tasks.

How to Make a Clear, Effective Course Change (Without Turning It Into a Mystery)

• Look out, then act: A good maneuver starts with scanning and sensing. If you spot potential risk, don’t hesitate. The sooner you begin a predictable turn, the less you risk confusion.

• Choose a deliberate course change: Aim for a change that’s easy to see and understand. A gradual nudge might look like a polite nod, but a more pronounced turn carries your intention with clarity. The critical piece is expectation management—your nearby mariners should be able to anticipate your new bearing without second-guessing.

• Communicate with signals: If you’re in a situation where signals matter, use them. Sound signals can reinforce your intent, and navigation lights or shapes (as appropriate) can help others read you, especially at night or in low-visibility conditions.

• Maintain situational awareness: Keep checking the other vessels’ movements as you maneuver. If someone else doesn’t react as you expected, be ready to adapt. The sea is a dynamic space; flexible thinking is a survival skill.

• Hold a safe track after the turn: Don’t snap back to a previous path too quickly. A stable, predictable path after your turn helps others settle into the new flow of traffic.

Mythbusters: Speed-Only Thinking Isn’t a Safe Shortcut

A common misconception is that slowing down automatically communicates “I’m yielding” or “I’m turning soon.” In practice, speed adjustments can be subtle and easily overlooked, especially when several boats are nearby or when eye contact isn’t easy. In some conditions, a slow-down is simply not enough to communicate a concrete intention. That’s why the rule emphasizes making the change obvious to others with a visible action.

Think about it like this: in a busy intersection with cars, a deceleration might be noticed, but a clear, early lane change signals your intent far more clearly. At sea, the same logic applies. You want your intentions to be legible without needing a lot of interpretation. A visible course change, especially when paired with proper watchkeeping and signaling, reduces the chance of misreadings.

A Quick Oceanic Toolkit: Signals, Rules, and Real-Life Tools

• Use the language of COLREGs: The Rules of the Road aren’t just laws; they’re a language that helps boats “talk” without shouting. The including principle about making your change obvious is part of the broader ethic of clear communication on the water.

• Signals matter: In many situations, sound signals (like warning blasts in certain conditions) and light signals help convey your plan. If you’re near others, complement your visual cues with appropriate signals to avoid confusion.

• Radar and AIS help, but they don’t replace human judgment: Technology can reveal speed, bearing, and range, but the human element—your readiness to act, and your clarity of intention—remains central.

A Quick Mental Model You Can Use

• If you’re unsure how your move will be interpreted, err on the side of a more obvious course change. In uncertain times, clarity trumps subtlety.

• When visibility is good and traffic is light, a well-timed speed adjustment can be enough. In thicker traffic or poorer conditions, favor a noticeable turn.

• Always pair your maneuver with a lookout and, when relevant, signals. A good move combines sight, signal, and space.

Real-World Takeaways You Can Use On the Water

• Clarity beats quietness. A direct, visible turn is a better communicator of intent than a mere slowdown.

• Predictability is safety. If others can forecast your path with minimal interpretation, your risk of collision drops.

• Practice makes confidence. The more you think about making your moves obvious, the quicker you’ll react with the right signal when it matters.

If you’re pondering a maneuver and the question pops back into your head—Should I slow down, or should I turn to show my intent? The answer, in the spirit of good seamanship, is to tilt toward a clear, noticeable course change when it’s the surest way to be understood. It’s not about making things dramatic; it’s about making them safe.

Final thoughts: navigation is the art of clear communication at sea. Your actions—the way you alter your heading, the signals you use, and the timing of your move—speak loudly enough for others to hear. When you choose a visible course change, you’re not just following a rule—you’re taking responsibility for the safety of everyone sharing your waterway.

Takeaways in brief

• Alter course when it makes your intention obvious to other vessels.

• In low visibility, with large or fast-moving ships, a visible turn is often safer than a mere speed change.

• Always pair any maneuver with vigilant lookouts and, where appropriate, signals.

• Strive for clarity, predictability, and safe spacing in every encounter.

Now you’ve got a practical lens for reading those COLREGs moments. Next time you’re in a crossing or meeting situation, ask yourself: is a clear course change the simplest way to keep the conversation on the water honest and safe? If the answer is yes, you’re probably on the right track.