Rule 27 requires anchored vessels to display an appropriate light and shapes for visibility

Anchor light 101: what Rule 27 really asks of you

Picture this: a quiet harbor at dusk, a small vessel resting on a calm line of water, and the other ships cruising by like ships in a bottle. It’s tempting to think once you’ve tied off the lines, you’re done with signaling. Not so. In the world of COLREGs, Rule 27 is all about visibility when a vessel is at anchor. The core message is simple, but it matters a lot: there must be an appropriate light and shapes to show other mariners you’re not moving.

Let’s unpack what that means in plain English—because the rules are there to keep everyone safe, not to trip you up.

What Rule 27 requires for anchored vessels

• The light: a white light visible all around the horizon. That means a 360-degree light, so sailors approaching from any direction can see you. It’s the beacon that says, “I’m here, I’m stationary, I’m protected from collisions.” The white color isn’t a fashion choice; it’s a universal cue for “anchored.”

• The shapes (day signals): a visual marker, commonly a black ball, that indicates the vessel is at anchor. In daylight, you’re signaling with a simple, identifiable indicator to help nearby boats gauge your status even when the air is calm but visibility isn’t perfect.

Why these signals exist—even if you’re just sitting quietly at the edge of a harbor

Think of the water as a crowded street after sunset. Boats are moving, zig-zagging, crossing paths. Without clear signals that you’re anchored, a fast approach from an unexpected angle could end badly. The white light acts like a lighthouse for nearby traffic, telling them to keep clear and pass at a safe distance. The day signal—your black ball—tells observers that you aren’t navigating; you’re holding steady, waiting for your next move or for conditions to change.

The “why” behind the signals isn’t just about rules on a page. It’s about practical visibility—especially when the night air is thick, fog creeps in, or rain dimples the surface of the water. In those moments, a bright, steady light and a simple day marker become a shared language between vessels. It’s not about theatrics; it’s about predictability and safety.

What you’ll typically see on the water

• Nighttime anchored vessels: a white light that shines all around the vessel. The goal is for any approaching boat to spot you from anywhere along the horizon and know you’re anchored.

• Daylight or clear conditions: a black ball as a day signal. Some mariners will use this alongside other signals in busy harbors, but the essential cue remains the same—“anchor status.”

A few practical nuances you’ll notice in real life

• Visibility isn’t a fixed promise. If you’re in an area with heavy traffic, you might also see additional markers or lights. Some skippers add reflectors or extra lighting to ensure they’re conspicuous even when weather isn’t cooperative. It’s smart, not flashy.

• You’ll hear stories from captains about batteries dying or lights failing. That’s why routine checks matter. A dead light is a blind spot for everyone, which can be risky. Regular maintenance isn’t glamorous, but it’s essential.

• In crowded harbors, you’ll sometimes encounter vessels that are anchored in channels or near fairways. In those spots, the signals can be even more important, since other boats might be maneuvering around them in tighter margins.

How to apply Rule 27 in everyday boating life

• When you anchor, set your white light clearly and check its visibility. If you’re near a busy lane or in poor weather, consider additional signaling or situational awareness to reduce risk.

• Place the day signal where it’s clearly visible to other mariners in daylight. A single black ball placed in a spot that’s easy to see from common approach angles goes a long way.

• Keep your watch, especially at night. A quick check that the light is on and the shape is visible can prevent a near-miss later on.

• Be mindful of wind and current. A buoyant anchor line, a shifting vessel, or a drifting position can change your signaling needs. If your situation changes—say, you pick a new anchorage—adjust signals accordingly.

What to do if you’re approaching an anchored vessel

• Slow down and give plenty of room. Even with lights and shapes, a moving vessel needs extra space when another boat is sitting anchored.

• Look for the anchor signal first. A white light and the black ball will tell you who’s anchored. If you’re unsure, reduce speed and keep well clear until you confirm.

• Communicate when appropriate. If you’re in tight quarters or restricted visibility, a short sound signal or a radio call to nearby traffic can help establish mutual awareness. It’s not mandatory for all encounters, but a courteous heads-up reduces surprises on the water.

A few caveats and common questions, answered

• Do all anchored vessels need both light and day shape? The rule emphasizes a white light for visibility and a day signal indicating anchor status. In practice, most vessels do both to maximize visibility, especially in busy waters or during darkness.

• What about fog or heavy rain? The light remains crucial, but in dense fog or rain, you’ll want to rely on additional signals, stay vigilant, and maintain a safe distance from moving vessels. The goal is obvious: be seen and be understood, even when conditions degrade visibility.

• Can a vessel at anchor use sounds too? Sound signals can supplement visibility, but they don’t replace the primary requirement of a visible light and day shape. Think of sounds as extra cues to reinforce the anchor status when sight lines are limited.

Anchoring well is a habit you’ll carry for a lifetime

I’ve spent evenings watching the harbor come to life—boats trickling in as the sun fades, lines slipping through chocks, and the quiet rhythm of anchors letting go. The technical side of Rule 27 is the backbone, but the real movie happens in the moment you’re anchored: you’re responsible for being predictable to others who share the water. A steady white light, a clear day shape, and a calm approach go a long way toward keeping the peace on the water.

If you’re new to the scene, here’s a quick, practical checklist you can tuck into your crew bag or your boat’s check-list binder:

• Before dropping anchor: inspect the anchor light. Make sure it’s clean, protected from spray, and visible in all directions.

• While anchored: confirm the white light is on and the ball (day signal) is displayed where it will catch the eye of approaching traffic.

• In changing conditions: if fog or heavy rain rolls in, re-evaluate your position and ensure your signals remain clearly visible. Consider slowing or repositioning to help others navigate safely.

• Regular maintenance: replace batteries, test bulbs, and replace damaged shapes or markers promptly. The signal is only useful if it’s working.

Why this matters beyond the page

Rule 27 isn’t just about a single light and a ball. It’s about a culture of visibility and courtesy on the water. When everyone understands that anchored vessels are signaling their status, the whole ecosystem becomes safer. It’s the difference between a tense near-miss and a calm, well-communicated moment that passes without incident.

If you ever find yourself dockside with a cup of coffee in hand, watching the harbor wake up, you’ll notice something practical: signaling isn’t a burden. It’s a shared language that helps boats of every size move smoothly around one another. The white light and the black ball aren’t flashy. They’re dependable, universally understood cues—like a pedestrian crossing sign for ships.

Final thoughts for steady, safe sailing

Anchoring is one of the most common maneuvers you’ll encounter. It’s also one of the moments when clear signaling matters most. Rule 27 keeps the waterway orderly by making anchored vessels visible, not just to the captain steering the wheel, but to every skipper who depends on good visibility to avoid a collision.

So next time you’re at anchor, pause for a moment and check your signals. A simple white light, a clear day symbol, and a watchful clock can turn a potentially tricky situation into a safe, predictable moment for everyone on the water.

If you’re exploring COLREGs more deeply, you’ll find many rules that weave together to create a safer seascape. Rule 27 is a reliable anchor in that tapestry—direct, practical, and essential for anyone who loves being on the water. And that makes it worth understanding, not just memorizing.