Not under command holds the highest position in the COLREGs vessel hierarchy.

Not under command tops the chart: why this COLREGs rule list matters more than you think

If you’ve ever stood at a helm or watched ships glide past a busy harbor, you know the sea doesn’t care about schedules. It cares about safety, space, and how quickly a crew can respond when something goes wrong. The Collision Regulations (COLREGs) lay out a hierarchy of vessel types and the responsibilities each one bears to keep collisions at bay. Among the common categories—fishing vessels, power-driven vessels, sailing vessels—a surprising line stands out: a vessel that is not under command has the highest priority in the hierarchy. That’s not a casual footnote. It’s a rule that keeps mariners safe when someone can’t move out of the way.

Here’s the simple idea behind the hierarchy: not all vessels are equally able to maneuver. Some are able to steer and brake at will, while others have limited or no ability to alter course or speed. In a tight situation, you want the decision-making to favor the boats that can actually change what they’re doing. That way, the most vulnerable and least able to respond aren’t forced into a collision because everyone assumed someone else would move.

So, which vessel is at the highest position? Not under command. That answer isn’t about labeling one ship as “the boss” in a boastful way. It’s about safety and predictability at sea. When a vessel can’t take action to avoid a collision—because it’s incapacitated, has a mechanical failure, or is otherwise unable to maneuver—every other vessel in the vicinity must give it the widest possible berth. It’s a duty, not a suggestion.

What does “not under command” really mean on the water?

Think of a vessel not under command as a car with bad brakes in the middle of a busy intersection. It can’t slow down or swerve to avoid the problem, so the other drivers must do everything they can to prevent a crash. In maritime terms, a NUC vessel cannot take any action to avoid a collision, even if it would be prudent to move. This could be due to engine failure, steering failure, or some other exceptional circumstance that has left the vessel unable to maneuver.

Because it can’t maneuver, a NUC vessel earns a special place in the COLREGs hierarchy. Other vessels must take “early and substantial” action to avoid, not just a polite turn out of the way at the last moment. The priority here is protection: when you’re the vessel with the power to adjust, you adjust early. When you’re the vessel that can’t, others must compensate—dramatically if needed—to prevent contact.

Now, where do fishing vessels, power-driven vessels, and sailing vessels fit in?

• Not under command (NUC): Highest priority. A NUC vessel cannot take action to avoid a collision, so others must maneuver decisively to keep clear.

• Fishing vessels: These are vessels engaged in catching fish using gear like nets or lines. They have their own set of obligations, especially when they’re maneuvering slowly or stopping to haul gear. They aren’t automatically protected by a blanket right-of-way—rather, their actions must still be coordinated with nearby traffic, and they may be called on to yield or keep clear depending on the scenario. In some situations, a fishing vessel may be required to refrain from impeding another vessel’s passage, particularly when another vessel is the stand-on or give-way vessel.

• Power-driven vessels: These boats rely on their engines to move. They’re generally more maneuverable than a NUC and can respond quickly to a developing situation. Still, they must respect the actions of others, especially a NUC, and take early action to avoid when necessary.

• Sailing vessels: Boats that primarily rely on sails for propulsion fall into this category. They can be slower to maneuver than modern power-driven craft, especially in light winds, so other vessels must account for their relative difficulty in changing course. Sail-powered craft aren’t exempt from rules; they just bring their own dynamic to every encounter.

Putting it into practice: what you do when you meet a NUC

The moment you realize you’re approaching a vessel that cannot maneuver, the rulebook kicks in. Here’s the practical mindset:

• Expect the unexpected. A NUC may be drifting or drifting more slowly than you anticipate. Don’t assume it will turn out of your way at the last moment.

• Start early: reduce your speed and alter your course well in advance to give yourself plenty of room. The goal is to have a safe margin, not to squeeze by just in time.

• Stay clear: keep well clear of the NUC’s intended path. If you’re crossing, you should adjust course to pass at a safe distance where you’re not relying on the other vessel to make a precise move.

• Communicate as needed: sound signals or radio communications can help establish intent and reduce confusion. Clear, decisive communication may save precious seconds in a close encounter.

• Don’t forget the other rules: even though the NUC has priority, you still must see and be seen. Maintain lookout, act with caution, and follow the standard traffic patterns for the area.

A quick mental model you can carry to the bridge

Let me explain with a simple image. Picture a busy intersection with three lanes of traffic, but one car has a flat tire and can’t move. The other cars aren’t free to dash through that intersection as they please; they must slow down, plan a safe path around the immobilized vehicle, and proceed with care. That’s the essence of a NUC on the water: it’s not a green light to bulldoze a path; it’s a signal to others to create the safe space needed to navigate around a vessel that’s out of action.

Common points of confusion, clarified

• Is a NUC the same as “not under command” only when the vessel can’t move? Yes. A NUC is defined by its inability to maneuver, not merely by a temporary malfunction in one system. It’s about overall command.

• Do other vessels always have to yield to a NUC? They must take early and substantial action to avoid, yes. But that doesn’t mean the NUC is exempt from any responsibility. The COLREGs require all mariners to act with due regard for safety, which means both sides have duties, but the priority rests with the vessel not under command.

• Can a sailing or fishing vessel ever outrank a NUC in a particular situation? No. In the hierarchy of maneuverability and safety, a NUC sits at the top because it cannot respond to danger.

Why this matters beyond a test question

The hierarchy isn’t a trivia exercise—it’s a safety framework that guides real decisions on the water. In crowded harbors, on coastal routes, or near busy shipping lanes, a capable crew must recognize a NUC at a glance and pivot quickly. The same applies to the other categories; every vessel type brings constraints and responsibilities. When you’re at the wheel, knowing where you stand in the order helps you act with confidence, not hesitation. It’s about reducing uncertainty in situations where nerves can run high and mistakes are expensive—sometimes deadly.

Digress a moment to the broader sea-dweller experience

If you’ve spent time near the coastline, you’ve probably noticed how sea life shapes our language as much as our laws do. “Give way” isn’t just a phrase; it’s a mantra for seamanship. The sea doesn’t reward swagger. It rewards readiness, patience, and a willingness to adjust course when the wind shifts. The COLREGs formalize that wisdom: if a vessel is not under command, everyone else must adapt. It’s a reminder that safety isn’t about who has the right of way in a given moment, but about who can avoid collision when the weather, the vessel, and the crew aren’t cooperating perfectly.

A practical takeaway you can apply anywhere

• Memorize the core hierarchy: Not under command has the highest priority. Fishing, power-driven, and sailing vessels have different maneuverability and obligations, but none outranks a NUC.

• Practice anticipation: in any encounter, think first about what could go wrong if the other vessel can’t move, and plan your course and speed accordingly.

• Keep the bridge a calm place: a little discipline—clear communication, steady hands on the wheel, and a readiness to slow down—goes a long way toward preventing incidents when the sea gets busy.

Closing thought: the sea rewards clarity

The truth about COLREGs isn’t that they’re a rigid set of rules to memorize; it’s that they’re a language for safety. The moment you understand that not under command means “I can’t move to avoid you, you must move,” you gain a powerful perspective on every encounter at sea. It’s not about who has the right of way in theory; it’s about making sure everyone makes it home safely.

If you’re curious to explore more about how collisions rules play out in different traffic situations—head-on, crossing, overtaking—you’ll find there are plenty of real-world examples and scenarios you can relate to. The more you see these principles in action, the more natural they’ll feel when you’re at the helm. After all, the sea isn’t a classroom; it’s your daily test, and clarity is the best kind of compass.