Sea marks are the “road signs” on the water – and a fixed part of the SBF See theory exam. Once you understand the system, you can derive almost any mark from its logic. In this article we explain the lateral system, the cardinal system and the most important special marks so you’ll recognize them confidently in the exam.
IALA Region A: The German System
Germany belongs to IALA Region A. This matters because the coloring of the lateral channel marks here is exactly reversed compared to Region B (North and South America, Japan). So the following rule applies to German waters.
The Lateral System: Channel Boundaries
Lateral sea marks mark the sides of a channel. The color tells you which side the mark is on – relative to the direction “from seaward” (toward the harbor / upstream).
Port Side: Red
- Color: red
- Shape (buoys): can / blunt-topped
- Topmark: red cylinder (can)
- Meaning: bounds the channel on the port side (left as you enter from seaward)
Starboard Side: Green
- Color: green
- Shape (buoys): conical / pointed
- Topmark: green cone, point up
- Meaning: bounds the channel on the starboard side (right as you enter from seaward)
Memory aid: “Coming in, red is on the left (port).” Green is then on the right (starboard) side.
The Cardinal System: Avoiding Danger
Cardinal marks tell you on which side you can safely pass a hazard. They are black and yellow and always carry two cones as a topmark – whose orientation reveals the compass direction.
North Mark
- Topmark: both cones pointing up
- Color: black on top, yellow below
- Meaning: pass the mark on its north side (safe water is to the north).
East Mark
- Topmark: cones base to base (looks like an egg / barrel)
- Color: black – yellow – black
- Meaning: pass on the east side.
South Mark
- Topmark: both cones pointing down
- Color: yellow on top, black below
- Meaning: pass on the south side.
West Mark
- Topmark: cones point to point (looks like a wine glass – “West = Wine glass”)
- Color: yellow – black – yellow
- Meaning: pass on the west side.
Memory aid for the topmarks: picture a clock – north on top (points up), south at the bottom (points down), west is the wine glass. The coloring follows the position of the black band: black on top = north, black below = south.
Other Important Marks
Safe Water Mark
- Color: red and white vertical stripes
- Topmark: a single red ball
- Meaning: “navigable water all around” – e.g. a landfall buoy. There is safe water on every side.
Isolated Danger Mark
- Color: black with one or more red horizontal bands
- Topmark: two black balls, one above the other
- Meaning: an isolated danger (e.g. a wreck) that you can pass on any side.
Special Mark
- Color: yellow
- Topmark: a yellow cross (X)
- Meaning: marks special areas (e.g. restricted zones, measuring stations, cable routes) – no pure navigational meaning.
Light Characteristics: “Reading” the Light
Many sea marks carry a light. The characteristic describes the rhythm and is abbreviated on the chart:
- Fl (Flashing): short flashes of light, longer dark phases
- Oc (Occulting): mostly light, short dark phases
- Iso (Isophase): light and dark phases equal length
- Q (Quick): rapid sequence of flashes – typical for cardinal marks
The light color often matches the mark color: red port buoys show a red light, green starboard buoys a green light.
Conclusion
The sea-mark system looks confusing at first but follows clear rules: in the lateral system, when entering, red is to port and green to starboard; the cardinal system shows the safe passing side via its cone topmarks; and special marks are yellow. Once you understand the logic, there’s hardly anything to memorize. In the Boatpass app you can train the sea-mark and navigation questions specifically with the official ELWIS catalog – including the typical exam images.