COLREGs · Rule 25 · 33 CFR §83.25
Sailing Vessels Underway and Vessels Under Oars
As of 2026-07-26: a sailing vessel underway shows sidelights and a sternlight — and nothing else that is mandatory. Under 20 metres those may be combined in one lantern at or near the top of the mast. She may optionally add two all-round lights in a vertical line at the masthead, red over green. Under 7 metres, if the prescribed lights are impracticable, it is enough to have an electric torch or lighted lantern showing a white light ready at hand, exhibited in time to prevent collision. A vessel under oars may use the sailing-vessel lights or fall back on the same white light.
What does Rule 25 actually say?#
Source
Practice this rule#
One real exam question on this rule, cited to source. No sign-up.
Under the Inland Rules, a sailing vessel of less than 20 meters may combine her sidelights and sternlight into one lantern carried ______.
How does Inland Rule 25 differ from COLREGs?#
Inland Rule 25 (33 CFR §83.25) carries the same lights as COLREGs Rule 25, so the light picture memorised for one rulebook reads the same in the other.
21 of 38 rules differ somewhere; the five the exam leans on are Rule 9, Rule 10, Rule 24, Rule 28 and Rule 34, side by side on Inland vs International Rules.
Why it shows up on the exam#
Two traps. First, the optional red-over-green is a sailing vessel, not a vessel restricted in her ability to manoeuvre — and it cannot be shown together with a combined lantern. Second, the under-7-metre and under-oars provisions are not “no lights required”: a white light must be ready at hand and shown in time to prevent collision. Note also what this rule does NOT cover — a sailing vessel under sail *and* engine is a power-driven vessel and shows the Rule 23 lights plus the Rule 25 forward cone, apex downwards.
What does the exam actually test here?#
The basic picture
Sidelights + sternlight
A sailing vessel underway exhibits sidelights and a sternlight. There is no masthead light — that is what distinguishes her from a power-driven vessel at night.
Under 20 metres
One combined lantern
The sidelights and sternlight may be combined in one lantern carried at or near the top of the mast where it can best be seen.
Optional signal
Red over green
A sailing vessel underway may additionally exhibit two all-round lights in a vertical line at or near the top of the mast, the upper red and the lower green. It is optional, and it may not be shown with the combined lantern.
Under 7 metres / under oars
White light ready at hand
A sailing vessel under 7 metres shall exhibit the prescribed lights if practicable; if she does not, she must show an all-round white light or have an electric torch or lighted lantern with a white light ready at hand, exhibited in sufficient time to prevent collision. A vessel under oars may use the sailing lights or the same fallback.
Rule 25 — common exam questions#
What lights does a sailing vessel show at night?
Sidelights and a sternlight, and no masthead light. Below 20 metres those may be combined into a single lantern at the top of the mast. The absence of a white masthead light is how you tell a sailing vessel from a power-driven one at night.
What do red over green lights mean on a sailboat?
They are Rule 25's optional identification signal for a sailing vessel underway — two all-round lights in a vertical line at the masthead, red above green, shown in addition to her sidelights and sternlight. They do not mean restricted in ability to manoeuvre (that is red-white-red under Rule 27), and they may not be combined with the single combined lantern permitted below 20 metres.
Does a dinghy or rowboat need lights?
It needs a light available, even if not fixed. A vessel under oars may show the sailing-vessel lights; if she does not, she must exhibit an all-round white light or have an electric torch or lighted lantern showing a white light ready at hand, to be shown in time to prevent collision. Same standard applies to a sailing vessel under 7 metres.
What lights does a sailboat show when motoring?
Those of a power-driven vessel under Rule 23 — masthead light, sidelights and sternlight — because a sailing vessel propelled by machinery is a power-driven vessel under Rule 3. By day, when proceeding under sail and machinery, she also shows a conical shape forward, apex downwards.
Authoritative source#
- 33 CFR §83.25 — this section with its neighbours. 33 CFR Part 83 is public domain; checked 2026-07-26.
- COLREGs Rule 25 is published by the IMO and is authoritative internationally.
Practise this rule against the real exam.
Real exam questions. No signup, no card.
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