Rule 11 explains how vessels in sight of each other must interact to keep navigation safe

Rule 11 in Plain English: Why seeing each other changes the game

On busy waterways, there’s a moment when two vessels lock eyes, so to speak. The moment they can see one another is when the COLREGs rules kick in in a meaningful way. Rule 11 isn’t about fancy maneuvers or long lists of do’s and don’ts; it’s the defining idea that sets the stage for everything that follows when ships, boats, and ferries share the same waterway. If you’ve ever wondered, “What’s the point of Rule 11?”, here’s the straight answer: it defines the scope, or the boundary, of when the other rules apply—precisely when vessels are in sight of one another.

Rule 11 in everyday terms

Let’s break it down so it sticks. Rule 11 says, in effect, that when two or more vessels are in sight of each other, the Rules of the Road apply to both of them. This is the boundary line: if you can see the other vessel, you must follow the standard rules that govern what each boat should do to avoid a collision. If you can’t see the other vessel, different considerations come into play, and the rules you’d follow in daylight might not be the same as those used when you’re navigating blind in fog. So Rule 11 is the compass that tells mariners, “Here’s when the usual collision-avoidance rules apply.”

Think of Rule 11 as the gatekeeper for interaction. It doesn’t teach you every possible move, but it tells you when to start applying the broader set of rules about right of way, give-way responsibilities, and safe speed. It’s not a backstage pass to every scenario, but it is the door you must walk through to have a proper, safe conversation on the water.

Walking through real-life scenes

Here are a few situations where Rule 11 matters most:

• Two vessels approaching each other in a crossing path. If both ships can see one another, the standard rules about who keeps course and who yields apply. The emphasis is on predictability and clear intentions. It’s not a free-for-all; it’s a dance with rules, not a freeform sprint.

• Overtaking in sight of the other ship. When you’re close enough to see the other vessel, you should follow the rules for overtaking, which usually means–in many cases–keeping clear and passing on the starboard side. Rule 11 makes sure both vessels know they’re under the same rules and aren’t guessing whether the other will move.

• Meeting in a crowded harbor channel. In sight of each other, you’re both bound to the same general principles: slow down, stay alert, and communicate your intentions with lights, sound signals, or radio if needed. The goal is simple: avoid confusion, avoid surprises, and keep things predictable.

These examples show why Rule 11 feels like common sense—once you’re able to see the other vessel, you’re both playing by the same deckhand’s rules. It’s the shared vocabulary of safe navigation.

Rule 11’s role alongside other rules

Here’s where the “in sight of each other” boundary really shines. Rule 11 isn’t the end of the story; it’s the starting line for the rest of Part B, the section that covers how vessels should act in a collision-avoidance context. Once Rule 11 confirms that two vessels can see each other, the usual suspects come into play: who gives way, who holds their course, how to maneuver in crossing scenarios, and how to overtake safely.

To be clear, heavy traffic management, night navigation, and speed limits aren’t all wrapped inside Rule 11 itself. Those topics live in other parts of the COLREGs. Rule 11 simply says, “If you can see the other vessel, you’re in the realm where these other rules apply.” It’s the foundation that keeps the rest of the rules coherent and enforceable in daylight, in glare, in choppy seas, and under the watchful eyes of other mariners.

Practical tips to anchor Rule 11 in your seamanship

Rule 11 is as much about habit as it is about law. Here are some practical angles to keep in mind:

• Always keep a diligent lookout. If you can see the other vessel, you’re in Rule 11 territory. If you ever lose sight, you should reassess and act according to the rules applicable to the new situation.

• Communicate clearly. Use the standard signals—sound signals if needed, appropriate lights, and, when practical, radio contact to reduce uncertainty. Clarity matters more than cleverness.

• Be predictable. Move at a steady pace, avoid sudden changes in direction, and give the other vessel enough time to understand your intentions.

• Respect the basics of safe speed and safe distance. The people who succeed in busy waters aren’t just fast; they’re careful, proactive about avoiding close calls, and ready to adapt as visibility changes.

• Use all available tools. Radar, AIS, VHF, and even the occasional binoculars aren’t ornaments; they’re part of the extended lookout that Rule 11 envisions when two vessels are in sight.

A gentle caveat about common misunderstandings

One tempting misstep is assuming Rule 11 means you can ignore the other rules if you can see the other vessel. Not so. Rule 11 doesn’t replace the rest of the rules; it makes them relevant. It says, “If you can see each other, you must operate under the standard collision-avoidance rules.” The right move is to apply the appropriate rule to the situation—whether crossing, overtaking, or meeting head-on—and then communicate your intentions so the other vessel isn’t left guessing.

A quick dive into the human side of Rule 11

Mariners aren’t robots. Even when the rules are crystal clear, weather, current, and fatigue can tilt judgment. Rule 11 acknowledges this human element by emphasizing the importance of visibility and mutual recognition. There’s a little theater in safe navigation: the glance, the acknowledged signal, the small turn of the rudder, the steady voice over the radio. It’s not theater for its own sake—it’s how crews build trust on a crowded waterway.

Related themes you’ll encounter on the water

• The value of a good lookout remains timeless. It’s not glamorous, but it’s the bedrock of safe navigation, especially when multiple vessels share a single channel.

• Lighting and signaling aren’t optional aesthetics. They’re essential cues that keep people aware of each other’s presence and intentions after dark or in fog.

• Education isn’t about memorization alone; it’s about applying a shared language. When two vessels can see one another, both parties benefit from a common understanding of what to do next.

Putting Rule 11 into the broader narrative of safe passage

Rule 11 might feel like a small piece of a larger puzzle, but it’s a pivotal one. It marks the point where “we can see them, so here’s how we behave.” Think of it as the seam that holds together a fabric of rules designed to prevent collisions in every imaginable scenario on the water. It’s practical, not ornamental. It’s a reminder that, in a world where visibility matters, the simplest agreements often save the day.

If you’re curious about how this all translates to real-world navigation, consider how fellow mariners describe encounters on coastal routes or in busy inland waterways. You’ll hear people talk about “seeing and being seen,” about making your intentions obvious, and about the shared duty to keep the channel orderly. That’s Rule 11 in action—an ordinary phrase for an essential principle.

Final thoughts: Rule 11 as a compass, not a checklist

So, what’s the true purpose of Rule 11? It’s the compass that tells you when you’re in the space where the general collision-avoidance rules apply. It’s the reminder that, once two vessels can see each other, you’re entering a zone where predictability, communication, and careful maneuvering are the norm. It’s about safety, yes, but also about the confidence you gain when you know both boats share the same expectations.

If you’re navigating the COLREGs with any seriousness, internalize this: Rule 11 isn’t the end of the road; it’s the opening line that frames every subsequent choice. When you’re on the water and you can see another vessel, you’re in a moment where clear thinking and calm, deliberate action matter more than anything else. That’s the heart of Rule 11—and the heartbeat of safe passagemaking.

Want to keep exploring the rules in a practical, down-to-earth way? Look into resources that detail how vessels decide who yields in crossing situations and how overtaking and head-on scenarios are handled when visibility is clear. The more you see how these pieces fit together, the more confident you’ll feel when you’re out there, eyes on the horizon and hands ready at the helm.