In restricted visibility, when two crossing vessels aren’t in sight, neither is the stand-on vessel

In fog or other restricted visibility, two crossing vessels that aren’t in sight both must act to prevent a collision. No vessel is designated as stand-on; focus on safe navigation, lookout, and timely evasive maneuvers per COLREGs for mutual safety at sea.

Fog draped the harbor like a thick quilt, muffling sound and shape. It’s one of those weather quirks mariners learn to read not with charts alone but with patience, discipline, and a little faith in the rules that keep traffic moving safely. When two vessels cross in that soup of gray, visibility so limited you can’t spot the other boat until it’s almost on your bow, which one stays steady and which one moves? The punchline is simpler than the suspense: neither vessel is designated as the stand-on vessel. Both must act to avoid a collision.

Let’s unpack what this means in practical terms, because the right understanding here isn’t about who has the “right of way” in normal conditions. It’s about staying safe when you can’t even see the other boat to decide who should move.

First: what the rules actually say about fog and crossing situations

In the open sea and in inland waters, the Rules of the Road—more formally, the International Regulations for Preventing Collisions at Sea (COLREGs)—set the ground rules for safe passage. There are clear sections about overtaking, head-on situations, and crossing situations. In a classic crossing, one vessel is on the other’s starboard side, and the rules prescribe actions depending on visibility and relative maneuverability.

But in restricted visibility—like fog—the situation gets trickier. The COLREGs emphasize maintaining a proper lookout at all times and using sound signals to convey your intentions when visibility is poor. The key twist in fog is not simply “who’s the stand-on vessel?” Instead, the safest move is for both vessels to err on the side of caution and to take early, substantial action to avoid a collision.

Why neither vessel is the stand-on in restricted visibility

In clear conditions, a stand-on vessel is the one that should hold its course and speed, allowing the other vessel (the give-way vessel) to take action to avoid a collision. The system works because both boats can see enough to interpret the other’s position and intention.

When visibility is restricted so you can’t see the other vessel at all, that whole dynamic dissolves. You don’t have a visual cue to interpret, and you can’t assume that the other boat knows you’re there either. The prudent approach is mutual vigilance and early maneuvering. In practice, both boats should be ready to adjust course or speed to prevent a crossing from becoming a near-miss or a true collision.

Think of it like driving in dense fog with a traffic signal that only sometimes flickers to life. You don’t rely on a bright green light (the stand-on role) as a guarantee—you slow down, turn on the fog lights, keep extra distance, and proceed with caution, expecting that others might not see you either. That mindset aligns with the spirit of restricted-visibility rules: cooperation, predictability, and extra visibility measures (sound signals, radar, extra lookout) to keep everyone safe.

What does this look like in practice on a vessel?

If you’re steering or acting as the helm, here are practical steps that reflect the mutual responsibility in fog:

• Heighten the lookout: In fog, the human lookout is more critical than ever. Assign additional lookouts if feasible, keep a constant watch for radar returns, and be ready to interpret ambiguous targets. The moment you suspect another vessel is nearby, you treat it as if it could appear anywhere—because in limited visibility, surprises abound.

• Use all available tools: Radar, AIS, VHF radio, and fog signals are your friends. Radar helps you track echoes even when you can’t see a vessel visually. AIS can inform you if another vessel is broadcasting its presence; radio communications can coordinate actions with a nearby vessel if there’s any doubt about intent.

• Sound signals: If there’s any doubt about another vessel’s location or maneuver, sound signaling becomes essential. A short blast or prolonged horn can alert nearby craft to your presence and intent, reducing the chance of a collision.

• Reduce speed and increase spacing: The default in fog is to slow down and increase the distance between you and other traffic. Think of it as adding margin for error. If you’re not sure where the other vessel is or what its plan might be, give yourselves room to breathe.

• Plan early, act early: Since you may not have clear sight of the other boat, you should anticipate potential crossings well in advance. If you’ll cross paths, start reducing speed or altering course at a safe distance rather than waiting until the last minute. Quick, decisive actions are more likely to avert danger in restricted visibility.

• Maintain a safe record of your actions: In fog, it’s often wise to document or at least mentally log the steps you took to avoid a collision. This isn’t about blame; it’s about clarity and accountability in the moment and afterward when you’re reviewing what happened.

The emotional pulse of fog navigation

There’s a palpable tension that fog brings to the bridge—an almost cinematic quiet, punctured by the occasional rattle of rigging and the murmur of the sea. You learn to read not just instruments, but the mood of the wind, the way the engine hums, the way your crew breathes a little easier when you’ve lined up a safe plan. It’s a situation where technical discipline meets human nerves, and the best crews blend those elements into a smooth, conscientious rhythm.

The same discipline shows up in the way you communicate. Short, clear messages help keep everyone aligned. If you have to switch course, say so in precise terms and verify it with your crew. If you need to slow to a certain speed, state it plainly and acknowledge when you’ve achieved it. In fog, every word matters—there’s less room for ambiguity, so you lean into direct, practical communication.

Why this matters beyond the fog box

More than a rulebook trivia moment, the no-stand-on-vessel-if-you’re-not-seen reality mirrors a broader principle in maritime safety: assume the other guy doesn’t see you. Being mistaken about what the other boat will do can be fatal. The paradox is simple but powerful: you stay safe not by clinging to a single role but by adopting a shared, cooperative approach to risk.

In calmer seas, the rules can feel almost wonky with their “rights” and “responsibilities.” In fog, they become almost humane. They remind you that safety hinges on perception, preparation, and mutual courtesy. You’re not just steering a vessel; you’re managing a moving field of uncertainty, translating instrument readings into a plan your crew can execute cleanly.

A few quick scenarios to anchor the idea

• Head-on meeting in the mist: You don’t assume one boat will stay on course. You both slow down and pass with ample distance, using sound signals to communicate your positions. If you’re uncertain about the other vessel’s status, you err on the side of caution and adjust course sooner rather than later.

• Crossing with poor visibility, neither vessel seeing the other: Both vessels should proceed with extreme caution, using radar and sound signals, and be prepared to alter course or speed to prevent a collision. The goal is to create a path with enough clearance so neither party feels pressured to take a last-minute, risky maneuver.

• One vessel has radar contact while the other doesn’t: The vessel with radar should share information promptly, if possible, and be ready to adjust as the other vessel’s position becomes clearer. But the key remains: act early and clearly to avoid confusion.

• Fog lifting gradually: Visibility improves, but you’re not out of the woods yet. Maintain a cautious approach, keep looking out, and resume standard crossing procedures only after you’ve confirmed mutual visibility and understanding of each vessel’s intended maneuver.

Bringing it home: the mindset that keeps everyone afloat

The bottom line isn’t about dominance or who’s on the starboard side. It’s about a shared responsibility to prevent collisions when you can only hear the other vessel through the fog, not see it. In restricted visibility, both vessels should be prepared to take evasive action, and neither should rely on a static stand-on posture. It’s a practical reminder that safety is a two-way street on the water.

If you ever find yourself navigating through dense fog, picture the sea as a crowded coffee shop in the early morning: people are moving slowly, you can barely make out the faces, and everyone’s trying to get where they’re going without bumping into each other. In that space, communication, slow pace, and steady, predictable moves are your best friends. The same holds true on the water. When you can’t see the other vessel, you listen harder, look longer, and act sooner—treating every crossing as a shared, collaborative effort to keep the waves peaceful and the journey intact.

So next time you sail into fog, remember: no one has a guaranteed stand-on position. The safest course is to anticipate, communicate, and adjust together. That’s the essence of navigating in restricted visibility—practical, human, and profoundly maritime. And if you keep that mindset, you’re not just following the rules; you’re honoring the oldest maritime instinct: look out for each other as the sea does—with quiet respect and a steady hand.