Learning the basics of colregs lights and shapes is usually fault boating that makes everyone's eyes glaze over until they're actually from a dark channel at 3 AM. It's one thing to check out a diagram inside a textbook, but it's a whole different story when you're looking at a cluster of flickering lights on the horizon and trying to figure out if that's a massive container ship or just an extremely confused fisherman.
The International Regulations for Preventing Collisions at Sea (COLREGs) can feel as if a legal headache, but they're basically just the "rules of the road" for the water. Since boats don't have turn signals or lanes, we make use of a specific system of colored lights at night and black shapes in the daytime to tell everyone else exactly what we are and what we're doing.
Why Do We Even Use These?
Imagine you're driving down a highway, but there are no lanes, no signs, and everyone is allowed to drive whatever vehicle they want, from a bicycle to a semi-truck. Now, do that in the dark. That's why we have these rules.
The lights and shapes tell you three main things: what sort of vessel it is, which way it's heading, and whether it's limited in how it can move. In case you see a vessel showing two red lights in a vertical line, you know they're "Not Under Command" (NUC), which is a fancy way of saying they've separated and can't get out of your way. If you didn't know that, you might keep heading straight on their behalf expecting them to turn.
The fundamentals of Nighttime Lights
At the most basic level, you've got your standard running lights. If you're on a power-driven vessel, you'll have a green light on the starboard (right) side, a red light on the port (left) side, a white masthead light, and a white stern light.
It's pretty simple: if you see a green light and a white light ahead, you're looking at the side of the boat crossing out of your left to your right. If you see red and green together, they're coming straight at you. And if you just visit a single white light? You're likely springing up behind someone and seeing their stern.
But it gets weirder when you add in sailing vessels. Simply because they don't have an engine running, they don't carry that forward-facing white masthead light. So, if you see red and green lights but no white light above them, that's a sailboat under sail alone. You're possibly the "give-way" vessel in this scenario, so look out.
Those Day Shapes You See Hanging in the Rigging
During the day, we swap the light bulbs for black geometric shapes. You've probably seen these dangling in the masts of larger ships or even some well-prepared smaller boats. They're usually made of heavy-duty plastic or foldable fabric.
The most common one is the black ball . If a boat is at anchor during the day, they're supposed to hoist one black ball where it can be seen. If you see three black balls in a vertical line, that boat is aground. It's basically a big "don't come over here" sign.
Then there's the cone . If a sailboat has its sails up but can also be using its engine, it's technically a power-driven vessel. To let everyone know, they ought to hoist a black cone with the point facing down. Honestly, a lot of recreational boaters forget this one, but it's a big deal for clarity in busy harbors.
Identifying the "Special" Vessels
This is where the colregs lights and shapes get a little more complex. Some vessels have "right of way" (though we technically call it being the "stand-on" vessel) because they're doing a job that makes it hard for them to move.
Fishing and Trawling
Commercial fishers have it tough. They have nets out that may span hundreds of feet. - Trawling: You'll see a green light over a white light at night ("Green over white, trawling at night"). During the day, each uses two cones with all the points touching, resembling an hourglass. - Other Fishing: If they aren't trawling but still have gear out, it's red over white ("Red over white, frying tonight").
Restricted in Capability to Maneuver (RAM)
These are the heavy lifters—dredgers, cable layers, or ships doing underwater work. They can't just swerve to miss you without ruining their work. - At Night: They show a "Red-White-Red" vertical sandwich of lights. - During the Day: They hoist a "Ball-Diamond-Ball" shape. If you see this, give them a very wide berth.
Vessels Constrained by Draft
Think of a massive tanker in a narrow channel. If they move a couple of feet to either side, they'll hit the bottom. They're stuck in their path. - During the night: Three vertical red lights. - During the Day: A black cylinder.
The Tugging and Towing Situation
Towing is another scenario that may get messy. In case you see a boat with two white masthead lights in a vertical line, they're towing something. If the tow is longer than 200 meters, they'll show three white lights.
A really important light to look for is the yellow towing light . This sits directly above the white stern light of the tugboat. If you see yellow over white, you know you're looking at the rear of a tug. Throughout the day, if the tow is long, both the tug and the vessel being towed will show a black diamond shape.
The biggest danger here is accidentally seeking to pass between a tug and its tow. That's an error you only make once. Always look for those diamond shapes or maybe the extra masthead lights before you decide to cut behind a slow-moving boat.
Easy Methods to Remember the Patterns
Let's be honest, memorizing all of this is a pain. Most sailors use little rhymes or mnemonics to keep it straight.
- "Red over Red, the captain is dead. " This helps you keep in mind that two vertical red lights mean the vessel is "Not Under Command" (broken down).
- "Red over White, frying tonight. " To fishing vessels (non-trawlers).
- "Green over White, trawling at night. " Pretty self-explanatory.
- "White over Red, Pilot ahead. " Pilot boats use this when they're looking for ships to guide into port.
For the shapes, it's a bit more visual. A diamond often indicates a "special" status or a tow. A ball usually means "stopped" or "stuck" (anchor, aground, NUC).
Practical Tips for the Bridge
When you're out there, don't just rely on your AIS (Automatic Identification System). AIS is great, but electronics fail, and plenty of smaller boats don't even have it. Your eyes are your best tool.
If you see a light and you aren't sure what it is, take a bearing. Watch it over a few minutes. If the bearing isn't changing but the light is getting closer, you happen to be on a collision course. At that point, it doesn't really matter if you've perfectly identified their day shape—you need to move.
Also, keep a pair of binoculars handy. A few of these lights can resemble a single blur from the distance. A quick look over the glass can reveal that "one" white light is in fact two masthead lights, telling you that the ship is much bigger than you first thought.
Wrapping Things Up
At the end of the day, understanding colregs lights and shapes is about communication. Since we can't always hop on the VHF radio and talk to every single boat we pass, these visual signals do the talking for us. They tell us who is busy, that is stuck, and who is just cruising along.
It takes some practice to spot these in the wild, but once you do, the ocean at night starts to feel a lot less like a dark void and a lot more like a busy, organized street. Just keep your lights clean, your shapes prepared to hoist, and always keep a sharp lookout. Safe sailing!