What 22.5 degrees abaft her beam means for the overtaking position under COLREGs.

What does "22.5 degrees abaft her beam" indicate about the overtaking vessel's position?

• A. The overtaking vessel can see the sidelights of the vessel being overtaken
• B. The overtaking vessel is able to see only the sternlight of the vessel
• C. The overtaking vessel is ahead of the vessel being overtaken
• D. The overtaking vessel is directly alongside the vessel being overtaken

Answer: (B)

"22.5 degrees abaft her beam" refers to the relative position of an overtaking vessel in relation to the vessel being overtaken. This specific angle indicates that the overtaking vessel is positioned off the wake of the vessel it is passing, more towards the stern than the beam. When the overtaking vessel is within 22.5 degrees from the stern of the vessel being overtaken, it means that the overtaking vessel will only be able to see the sternlight of the vessel being overtaken. This visibility confirms that the overtaking vessel has not yet passed the other vessel and is still approaching from behind. Understanding this aspect of the navigation rules is crucial. When a vessel is overtaken, the overtaken vessel should only see the sidelights and possibly the masthead lights of the overtaking vessel once it is sufficiently ahead. Therefore, the scenario presented aligns with the visibility rule that specifies the other vessel's sternlight would be visible when the overtaking vessel is within that specific angle.

Outline / Skeleton:

• Hook: lights, angles, and the moment you realize what a single degree can mean on the water.

• Core concept: what “22.5 degrees abaft her beam” means for an overtaking vessel.

• Answer and explanation: the correct option is that the overtaking vessel can see only the sternlight.

• Visualize it: map the positions with simple geometry and light cues (sternlight vs sidelights) to build intuition.

• Why it matters in real life: safe, predictable passing under COLREGs; what each party should see and do.

• Practical takeaways: quick mental checks on board, tips for night or fog, and a few light-hearted analogies to keep the concept sticky.

• Wrap-up: a friendly nudge to practice this mental image whenever you’re near other vessels.

What does 22.5 degrees abaft her beam actually mean?

Let’s set the scene. You’re steering or watching from the bridge, and you hear a phrase you’ll hear a lot in COLREGs discussions: 22.5 degrees abaft her beam. Put simply, it’s a way of saying where the overtaking vessel sits relative to the vessel being overtaken.

The multiple-choice question you’ll see a lot goes like this:

• A) The overtaking vessel can see the sidelights of the vessel being overtaken

• B) The overtaking vessel is able to see only the sternlight of the vessel

• C) The overtaking vessel is ahead of the vessel being overtaken

• D) The overtaking vessel is directly alongside the vessel being overtaken

If you’ve got a copy of the rules handy, you know the right answer is B: the overtaking vessel is located in a position where it can see only the sternlight of the vessel being overtaken. Why is that the case? Because 22.5 degrees abaft the beam puts the overtaking vessel just behind the other vessel’s side, leaning toward the stern. In that slice of the sky, the sidelights—the red and green lamps on the bow sides—are mostly hidden from view, and you’d primarily pick up the sternlight, which glows behind on the boat’s tail.

Here’s the mental image that helps me keep it straight: imagine a clock face on the side of the overtaken vessel. The beam corresponds to 3 o’clock (port) and 9 o’clock (starboard). “Abaft” means toward the 6 o’clock direction—the stern. So 22.5 degrees abaft the beam is a small step toward 6 o’clock from the 3 or 9 o’clock line. From there, the overtaking vessel is effectively behind and off to the side, not fully to the vessel’s side or directly behind it. That small angular window is enough to shift what lights you can reliably see.

A quick geometry recap (without the math headache)

• The centerline of a vessel is the 0-degree line forward.

• The beam is 90 degrees to either side.

• “Abaft” moves you toward the stern from the beam line.

• At about 22.5 degrees behind that beam, you’re not seeing the side lanterns clearly anymore; you’re mostly catching the sternlight.

This is more than trivia. It’s a cue about who should see whom and who should slow down or steer clear.

Why this matters under the Rules of the Road

COLREGs are, at their core, a language of signals and predictability. When two vessels come into a passing situation, the lighting and the relative position tell both crews who has the right of way, who should keep clear, and how to steer to avoid a collision.

• If you’re the overtaking vessel and you’re at 22.5 degrees abaft the beam, you’re still approaching from behind. You haven’t visibly overtaken yet, and you should continue to keep well clear.

• If you’re the vessel being overtaken, you’ll see the overtaker’s sidelights as they come up the side. But when the overtaker sits within that 22.5-degree aft angle, your best visual cue might be only the sternlight—so you can’t rely on seeing a full pre-overtake signal from that angle.

The practical upshot: speed, distance, and timing stay in the driver’s seat. If you’re the overtaker, you’re inching past, not carving out a path to collide. If you’re the vessel being overtaken, you’re watching for the moment the other boat disappears from your stern light and becomes a clear pass to your starboard or port side.

A few real-life notes to keep in mind

• Visibility changes with the weather. Fog, rain, or haze can reduce the clarity of those lights. In tricky conditions, extra caution is a smart habit.

• Nighttime adds another layer. It’s easier to misinterpret a starboard/port light if you’re scanning with fatigued eyes. A brief, deliberate scan of the horizon and a quick check of the sternlight can save you from a near-miss.

• Sea conditions matter, too. A lumpy sea or a following swell can shift your apparent position. The 22.5-degree rule helps you estimate a safe clearance, but never rely on sight alone—keep a mental buffer and use all available instruments.

Let me explain the practical seating chart on the water

Think of the other vessel as a moving chart on your radar or lookout. When you are behind and slightly off the side, the starboard or port differences become less obvious from the overtaking perspective. That’s when the rule about lighting shines. If the overtaking vessel can only see the sternlight, you’re in that exact window where you haven’t yet cleared the other vessel’s stern and aren’t in a fully parallel pass yet.

This is a good moment to connect light cues with behavior:

• Sternlight visible: you’re behind and near the stern, still approaching. Keep clear and adjust speed to pass safely.

• Sidelights visible: you’re near the vessel’s side and still not past. The overtaking vessel may be closer to the flag in the sails of the water, but you should expect a controlled, orderly pass.

• Both sidelights visible: you’re more aligned with the beam and you’ll likely see the other vessel in a more “head-on or crossing” posture, which changes how you respond. But in a true overtaking scenario, you typically don’t want to reach this angle while the overtaking is underway unless you’ve planned the maneuver carefully.

Small, human moments that make the rule feel real

• Picture this: you’re piloting a small cruiser along a quiet channel at dusk. The other boat appears just behind your stern, its lights creeping into view. If you’re the overtaking craft, you’re likely thinking about easing off the throttle a touch and letting the other boat drift past, keeping clear until you’re well clear. If you’re the one being overtaken, you’re focused on maintaining your course and speed so the other vessel can pass smoothly.

• It’s a good reminder that nautical rules aren’t just about right and wrong; they’re about predictability and courtesy on a busy water, much like lane rules on a highway—just with more spray and fewer road signs.

A few takeaway tips you can use

• When you’re near another vessel, anticipate the lighting cues you’ll see. If you’re behind and off to the side, expect to catch the sternlight first.

• Always give space during overtaking. If you’re unsure whether you’ve passed, err on the safe side and wait a bit longer.

• At night, take a quick moment to scan for sternlights and sidelights in a circular sweep. A pause in motion can prevent a hit.

• Use sound signals sparingly but decisively when visibility is poor or when your intentions aren’t obvious. A deliberate horn blast can clarify that you’re passing, not colliding.

• Practice mental pictures of angles throughout your ride. It’s a simple habit, but it sticks when you need it most.

A friendly way to translate theory into a confident crew

The beauty of the COLREGs is their practical, almost tactile nature. The phrase “22.5 degrees abaft her beam” isn’t a math test; it’s a compass for safe seamanship. The moment you can translate that angle into what you can see—sternlight vs sidelights—it becomes a real-world tool. It helps you decide when to pass, who yields, and how to steer to keep everyone on board and on course.

If you’re new to this kind of thinking, you’re not alone. A lot of mariners—beginners and seasoned hands—learn by mixing words, diagrams, and hands-on practice. A simple mental map, a quick glance at lights, and a steady pace often do more than a long frenetic lecture. The water rewards calm, clear thinking, and consistent rules.

A final thought

Light, angle, and distance—these aren’t just abstract terms. They’re the everyday language of the sea. When you hear a description like “22.5 degrees abaft her beam,” you’re getting a snapshot of a moment on the water where two vessels negotiate space, predict each other’s moves, and glide past with safety and confidence.

If you ever find yourself at the helm and the sun dips low, and the lamps of another boat begin to glow, take a breath. Picture that clock-face, map the angle in your head, and let the sternlight tell you what to do next. The rules aren’t there to trip you up—they’re there to keep you and everyone else afloat, calmly and confidently.

In short: 22.5 degrees abaft her beam points to a position where the overtaking vessel can see only the sternlight, signaling a moment just behind and to the side of the vessel being overtaken. It’s a small angle with a big responsibility, and with practice, it becomes second nature—like riding a bike, only with more wind and less gravel smack.