Rule 23 · USCG Navigation Rules
Air-cushion vessel (non-displacement mode)
A hovercraft skimming on its cushion adds an all-round flashing yellow light to the normal power-driven lights.
Viewpoint
Display
Drag to orbit freely, scroll or pinch to zoom — or use the viewpoint buttons above (keyboard friendly).
From the port bow you see:
- All-round flashing yellow (flashing)
- white — Masthead light
- red — Port sidelight
→ Air-cushion vessel (non-displacement mode) — Non-displacement mode, seen from the port bow.
Memory aid
“Hovercraft hustle: flashing yellow = riding the cushion (non-displacement).”
What it means
Non-displacement mode
In displacement mode she shows only the normal power-driven lights — the flashing yellow means she is riding her cushion and may not behave like a displacement hull.
Day shapes
No special day shape — by day this vessel is recognised by sight, not by shapes.
Light details
| Light | Colour | Arc | Position |
|---|---|---|---|
| All-round flashing yellow | yellow (flashing) | 360° all-round | Mast, vertical line (top) |
| Masthead light | white | 225° forward | Forward masthead position |
| Port sidelight | red | 112.5° to port | Port side, deck level |
| Starboard sidelight | green | 112.5° to starboard | Starboard side, deck level |
| Sternlight | white | 135° aft | Stern |
2D profile
Labelled side view — works without WebGL and in print. Variant shown: Non-displacement mode.
In fog, she sounds
Don’t confuse with…
Official source
Rule 23, reproduced from the public-domain COLREGs Rule 23(b) — USCG Navigation Rules. Diagrams and 3D scenes are original to boatrules.com.