Study by Images
Browse each vessel type with fixed-aspect 3D models, matching 2D light diagrams, and day/night controls.
23Power-driven vessel underway
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An interactive 3D illustration is shown here. The same content is described in the rule text and key takeaways below.
2D light grid
Power-driven vessel — two masthead lights shown (required at ≥50 m; also permitted below 50 m)
5 lights
Power-driven vessel — one masthead light shown (option for vessels <50 m)
4 lights
Power-driven vessel < 12 m — simplified
3 lights
Power-driven vessel <7 m, maximum speed ≤7 kn — white light; sidelights also required if practicable
1 lights
Air-cushion vessel, non-displacement mode
5 lights
WIG craft taking off, landing, or IN FLIGHT near the surface
5 lights
How to learn vessel lights and day shapes with 3D models
Study selected light and day-shape configurations from Rules 23–30. Compare the four aspects and check the vessel type, length and operating condition against the rule. A visible pattern alone may fit more than one situation.
Use the rule arrows, variant controls and four viewing aspects to compare the selected arrangements. The 2D grid shows the variants alongside the 3D viewer.
Once the patterns feel familiar, switch to the image-based test, where the same vessels appear unlabelled and you identify them by their lights alone.