If there’s any doubt about collision risk, use all means to assess and determine danger.

When there’s any doubt about the risk of collision, the move is simple, but powerful: use all means to assess and determine the risk. That line comes straight from the discipline of COLREGs, the international rules that keep ships from bumping into one another. It’s not about one tool or one sense; it’s about gathering every bit of information you can and making a clear, informed decision quickly. Think of it as a safety net made of radar pings, AIS echoes, charts, and good old-fashioned lookout.

Let me explain why this matters. Humans are excellent at noticing things visually, but our eyes aren’t perfect, especially when you’re on a rolling deck, in fog, rain, or a crowded harbor. A lot of risk hides in the gaps between what we can see and what we can measure. Maybe you spot a glimmer of metal at the edge of your searchlight, maybe the bow wave looks like a mere wake, or perhaps you’re staring at a target that seems to be on a safe bearing—yet something feels off. That “feels off” moment is the signal to widen your view, not to tighten it. That’s what using all means is really about: expanding your awareness until risk becomes obvious.

What exactly counts as “all means”? Here’s the practical toolkit, without the jargon trap:

• Visual observations (your eyes, binoculars, and the human lookout). Yes, still essential, but not the sole source of truth.

• Radar and radar plotting. Use range, bearing, and closure rate to determine how quickly two vessels are approaching. Pay attention to any changes in target speed or course.

• Automatic Identification System (AIS). It gives you the other vessel’s course, speed, and sometimes type. Don’t trust it blindly—verify against what you see on the water and on your charts.

• Electronic navigation systems (ECDIS, chartplotters) and your chart. Cross-check the vessel’s position with the charted depth, traffic lanes, and navigational risks.

• Sound signals and VHF communications. A brief whistle or fog signal can reveal intentions or clarify who is maneuvering. A quick call on VHF Channel 16 can prevent miscommunication.

• Speed, course, and bearing changes. Crunch the numbers quickly: what’s the closest point of approach (CPA)? How soon will you be at that point? What about the time to the closest point (TCPA)?

• Environmental factors. Current, wind, visibility, and water depth—these all affect how a risk develops.

If you’re ever in doubt, the best move isn’t to blink or to look away. It’s to run through a simple, deliberate sequence of checks. Start with your eyes and your eyes again—then bring in the instruments. If anything doesn’t align, act early.

A simple decision-making sequence you can follow at sea

1. Confirm the target. Locate the other vessel on radar and visually. Do the radar and AIS reports match what you see? If there’s a discrepancy, treat it as a potential risk until it’s resolved.

2. Quantify the risk. Calculate or estimate CPA and TCPA. If the CPA is closing quickly or if bearing is narrowing, that’s a red flag.

3. Check all sources. Compare AIS data with the chart and actual position. Check wind and current that might push you closer or farther away than you expect.

4. Communicate clearly. If you determine there’s a risk, broadcast a short, unambiguous message on the appropriate channel. Tell the other vessel who you are, what you’re observing, and what you intend to do if needed.

5. Change course or speed decisively. If necessary, alter your bearing to starboard or reduce speed to increase time and distance, giving both vessels breathing room.

6. Monitor after the action. Keep a watch on the other vessel’s response and re-evaluate CPA/TCPA after you’ve adjusted your plan.

7. Document the decision in your mind and, if possible, in your log. Even small, routine decisions matter when multiple targets are in play.

Why not rely on a single tool? Because every method has blind spots. Visual sight can be hampered by glare or weather. AIS can fail, be misreported, or be spoofed in rare cases. Radar might show clutter or a confusing echo in rough seas. By combining all available means, you slow the chance of a nasty surprise and you build a safer margin.

Think of it like driving in a busy city at dusk. You don’t pull up behind the wheel, switch on your headlights, and then assume every pedestrian will appear exactly where you expect. You use your headlights, you scan the sidewalks, you listen for horns, you watch the brake lights ahead, and you keep your hands ready on the wheel. You’re not doing this to prove a theory; you’re doing it to stay out of harm’s way. The water isn’t a straight road. It’s a dynamic, sometimes chaotic space, where risk can materialize from a momentary lapse in attention or a misread signal.

Common traps that slip into the harbor of complacency

• Assuming there’s no risk because you saw no obvious threat. Silence isn’t proof of safety; risk can hide behind a small, fast-moving vessel, or in a blind spot along your starboard bow.

• Relying on one source of information. A lone radar blip can become a ghost target if you don’t cross-check with AIS and visual lookout.

• Waiting for the other vessel to signal first. The other party might not realize you’ve got a problem or might delay; proactive assessment reduces delay and confusion.

• Overlooking weather and currents. Even with good radar, a strong current can push you into a risk zone if you don’t account for it.

• Fixating on a single bearing or course. If you fixate, you might miss a subtle but significant change in a target’s path.

In COLREGs terms, what we’re really doing is applying Rule 7: Risk of collision. The rule says you should assess whether a risk exists and take action if there is one. It’s not a suggestion; it’s a fundamental safety responsibility. And the most responsible approach is to do so with every available means. When you doubt, act early and decisively.

Real-world flavor: imagine a commercial vessel nearing a busy harbor entrance. The radar shows several echoes, one of which seems to be on a close cross path. AIS indicates a vessel on a similar course but at a different speed. The weather is hazy, with a light drizzle that blurs the far horizon. In that moment, you don’t wait for a perfect, crystal-clear signal. You pull in all the tools: confirm the target’s range and speed with radar, verify its course with AIS, check your chart to ensure you’re not entering a shallow channel, listen for any fog signals, and, if needed, send a brief VHF message to the other vessel to clarify intentions. Then you adjust your own speed and course to reduce the risk. The result isn’t luck; it’s disciplined seamanship built on using every available means.

A few practical tips for staying sharp

• Maintain a robust lookout even during routine passages. The best “tool” is a trained, vigilant crew member who’s not glued to one device.

• Regularly cross-check data sources. If your AIS shows a target, make sure the target’s position aligns with radar and the chart.

• Practice early action. If CPA/TCPA suggests danger, don’t wait for the other vessel to move first. Small changes now can prevent big problems later.

• Keep your equipment in good shape. A clean radar screen, a functioning AIS, and up-to-date charts save seconds when it matters.

• Use conversations as a tool, not a distraction. A quick, clear exchange with a nearby vessel can avert a near-m miss and reduce tension on the bridge.

What this means for you at sea

The rule to use all means to assess and determine risk isn’t a dry instruction; it’s a mindset. It’s about staying curious, staying cautious, and staying coordinated with the other boats that share the water. It’s about turning information into action—fast, precise action that buys you time to maneuver safely and keeps crew, cargo, and vessels out of harm’s way.

If you’re new to this way of navigating, the key takeaway is simple: don’t settle for the first impression. Build a fuller picture by pulling in every available signal. It’s a practice that pays off whether you’re skimming along a coastal lane in calm weather or threading a killer current through a congested harbor at dusk.

The bottom line

When there’s any doubt about collision risk, act with confidence and thoroughness: use all means to assess and determine risk. Visuals, instruments, signals, and sound all work together to create a clearer map of danger. That’s how safe navigation becomes second nature, not something you think about after the fact.

Takeaway guide to remember:

• Don’t rely on one source. Cross-check everything.

• Calculate CPA and TCPA, but don’t wait for a perfect number—use it to guide your decision.

• Communicate clearly and early with other vessels.

• Adjust course or speed as needed, and monitor the situation afterward.

• Keep the lookout sharp and the equipment in top form.

Cornerstone thought: safe navigation isn’t a single trick; it’s a disciplined habit of gathering information, interpreting it, and acting decisively. The sea isn’t asking for perfection; it’s asking for thoughtful, prepared seamanship. And when doubt arises, the right move is to cast a wider net, and let all the tools do their part to keep everyone aboard safe.