Rule 27 · USCG Navigation Rules
Small vessel engaged in diving operations
Too small for the full dredging shapes: red-white-red all-round lights by night, a rigid replica of Code flag 'A' by day.
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 red (top)
- All-round white (middle)
- All-round red (bottom)
→ Small vessel engaged in diving operations — Divers down, seen from the port bow.
Memory aid
“Red-white-red with flag 'A' flying — divers below, keep clear and slow.”
What it means
Divers down
By day: a rigid replica of International Code flag 'A' (white-and-blue swallowtail) at least 1 m high, visible all round — flags are not part of the day-shape set here, so it is described rather than drawn. Note the Rule 27(g) small-vessel exemption does NOT apply to diving operations.
Day shapes
No special day shape — by day this vessel is recognised by sight, not by shapes. Exception in practice: a small dive boat flies a rigid replica of International Code flag “A” (white and blue, swallow-tailed), at least 1 m high and visible all round — flags are described rather than drawn here.
Light details
| Light | Colour | Arc | Position |
|---|---|---|---|
| All-round red (top) | red | 360° all-round | Mast, vertical line (top) |
| All-round white (middle) | white | 360° all-round | Mast, vertical line (2nd from top) |
| All-round red (bottom) | red | 360° all-round | Mast, vertical line (3rd from top) |
2D profile
Labelled side view — works without WebGL and in print. Variant shown: Divers down.
In fog, she sounds
Don’t confuse with…
Official source
Rule 27, reproduced from the public-domain COLREGs Rule 27(e) — USCG Navigation Rules. Diagrams and 3D scenes are original to boatrules.com.