Red to port, green to starboard, coming in from seaward: most SBF See candidates pick up this basic rule of the lateral system quickly. But what does “from seaward” actually mean when a channel connects two different sea areas, or when there are no tides to orient yourself by at all? This is exactly where the North Sea and the Baltic Sea differ noticeably, and it’s a favorite topic in the exam. This article explains how the direction of buoyage is actually determined and why you should check the chart more often in the Baltic than in the North Sea.

The Basic Rule: Buoyage “from Seaward”

In the lateral system of sea marks, Germany, as part of IALA Region A, follows a simple color code: port-hand marks are red, starboard-hand marks are green. Which side counts as port and which as starboard depends on an assumed direction of travel, the so-called direction of buoyage. The basic rule here is the direction “from seaward” or upstream, meaning the direction a vessel takes when entering a harbor, river mouth, or cruising area from the open sea.

Buoys also carry numbers for orientation: starboard-hand marks get odd numbers, port-hand marks get even numbers, and the numbering increases in the direction of buoyage. Comparing the current buoy number with the previous one tells you which way the buoyage runs, even without reading your direction of travel off the chart.

This basic rule sounds simple, but it assumes there is a clear “from seaward” to begin with. That’s exactly where the difference between the North Sea and the Baltic Sea starts.

The North Sea: Tides Provide the Direction

Along the German North Sea coast, the direction of buoyage is usually intuitive. The North Sea is a tidal sea with a pronounced tidal range, and river mouths such as the Elbe, Weser, or Ems are regularly flooded and drained by incoming and outgoing water. The direction “from seaward” coincides here with the natural direction of travel, in which a vessel rides the flood tide from the open sea toward the harbor or upstream. That’s why the direction of buoyage in most North Sea channels reveals itself almost automatically, once you know where “sea” is and where “land” or the harbor is.

This doesn’t mean everything in the North Sea is automatically unambiguous. In the branching channels of the Wadden Sea in particular, with their many tidal creeks and secondary channels, it’s always worth checking the chart, since not every tidal creek clearly leads “from seaward” or “toward land”; some connect two channels with each other. But the general logic of “from seaward toward land or harbor” gives you a reliable first orientation almost everywhere here. You can read more about the tides themselves in the article on the rule of twelfths.

The Baltic Sea: No Meaningful Tides, No Natural Direction

The Baltic Sea, by contrast, has virtually no tides in the sense of a regular, pronounced tidal range. Changes in water level here are mostly caused by wind and air pressure rather than the lunar influence that drives the North Sea. Along long stretches of the Baltic coast, this means the natural current direction that buoyage relies on in the North Sea simply isn’t there.

For individual harbor approaches and river mouths on the Baltic, the direction is usually still obvious: “from seaward” toward the harbor or river mouth applies here too. It gets more difficult where a channel connects two sea areas, or where it’s genuinely unclear which of the two sides counts as “seaward”, for example in bays, the shallow lagoon waters typical of the German Baltic coast (Bodden), or canal and passage stretches. There’s no tide-driven preferred direction to settle the question automatically.

When the Direction Isn’t Obvious: The Chart Decides

For exactly these ambiguous cases, whether in the Baltic, in canals, or anywhere else without an obvious natural direction, the responsible authority fixes the direction of buoyage and marks it on the official nautical chart with a dedicated arrow symbol. This symbol tells you directly which way the buoyage is “intended” to run, regardless of which way you’re actually sailing.

In practice, this means: while you can usually trust your instinct for “from seaward” in clear-cut North Sea channels, you should actively check the chart for how the direction of buoyage is defined in potentially ambiguous Baltic channels. How to read a nautical chart in general is covered in detail in the article How to Read a Nautical Chart.

The Kiel Canal as a Clear Example

The topic becomes especially tangible at the Kiel Canal (Nord-Ostsee-Kanal), which literally connects the two seas in question. The buoyage and buoy numbering of the canal follow a fixed direction from the North Sea side at Brunsbüttel to the Baltic side at Kiel. So if you’re sailing from Brunsbüttel toward Kiel, the port-hand buoys are, as expected, on your left. If you’re sailing from Kiel toward Brunsbüttel, however, you’re moving against the defined direction of buoyage and need to mentally flip your reasoning: the red buoys are then on your right, the green ones on your left. This principle, a fixed, defined direction independent of your own heading, is exactly what sets the North Sea and Baltic Sea apart when it comes to buoyage.

Why the Direction of Buoyage Matters in Practice

The direction of buoyage is more than a memory aid for the exam; it structures traffic in a channel much like a two-lane one-way system. Knowing which way the buoyage is “meant” to run also helps you judge where to expect oncoming or overtaking traffic, and which side you should keep to in order to follow the general keep-to-starboard practice in narrow channels. How the give-way and right-of-way rules on the water actually work is explained in the article Right of Way and Collision Rules. Especially in narrow, busy channels, such as approaches to major harbors or canals, misreading the direction of buoyage can quickly put you on the wrong side, with a corresponding risk in meeting situations.

More Examples: Bays and Lagoon Waters of the Baltic

Beyond canals, ambiguous situations on the Baltic also show up in larger bays, sound areas, and the lagoon waters (Bodden) typical of the region, for instance where several channels meet or a body of water can be entered from two different sides. For skippers used to the North Sea, this often feels unfamiliar, since there the direction is usually obvious at a glance. On the Baltic, it’s worth making a habit of checking the direction of buoyage for your planned route on the chart before you cast off, rather than guessing it underway. This applies especially to areas you don’t know well yet.

What Stays the Same Between the North Sea and the Baltic

As significant as the difference in buoyage direction is, almost everything else about the system is identical along both German coasts:

  • Colors and shapes of lateral marks are the same everywhere: red with a blunt shape on the port side, green with a pointed shape on the starboard side of the direction of buoyage.
  • The cardinal system, with its black-and-yellow marks and characteristic cone topmarks, works identically in the North Sea and the Baltic, independent of the direction of buoyage, since cardinal marks always refer to compass direction.
  • Special marks, safe water marks, and isolated danger marks are likewise regulated consistently; more on this in the article on the sea-mark system.
  • Buoy numbering increases in both sea areas in the direction of the respective defined buoyage, odd numbers to starboard, even numbers to port.

The difference, then, isn’t in the system itself, but purely in how easily you can work out the direction the system refers to from your surroundings.

Common Exam Pitfalls

In the SBF See theory exam, the direction of buoyage is often tested using chart excerpts where you have to work out for yourself whether a buoy lies to port or starboard. Common pitfalls include:

  • Automatically applying North Sea logic to the Baltic, even though there’s no clear natural direction at that particular spot and the chart notation applies instead.
  • Mixing up port and starboard when your own direction of travel is opposite to the defined direction of buoyage, as in the Kiel Canal example from Kiel to Brunsbüttel.
  • Ignoring the direction-of-buoyage arrow symbol on the chart at points where two channels or two sea areas meet.
  • Jumping to a direction of buoyage based only on your compass heading, even though your own course says nothing about which direction the buoyage of the channel you’re in is actually defined to run.

Once you’ve internalized that the direction of buoyage doesn’t always match your own heading, but is a fixed reference recorded on the chart, you’ll fall into these traps far less often.

Conclusion

The lateral system itself is identical in the North Sea and the Baltic; colors, shapes, and topmarks don’t differ. The decisive difference lies in the direction of buoyage: in the tidal North Sea, the “from seaward” direction usually emerges naturally from the tidal flow, while in the nearly tideless Baltic, that natural orientation is missing in many places, which is why the authorities fix the direction there and mark it on the chart with a dedicated arrow symbol. Once you’ve internalized that, you’ll read chart excerpts more confidently in the exam, and you’ll be less surprised in real channels when port and starboard suddenly sit differently than expected. In the Boatpass app, you can train exactly these kinds of buoyage chart questions with the official ELWIS question catalog, separated by SBF Inland and SBF Coastal.