Sailing Vessels Underway and Vessels Under Oars

Rule text#

(a)A sailing vessel underway shall exhibit:

(i)Sidelights; and

(ii)A sternlight.

(b)In a sailing vessel of less than 20 meters in length the lights prescribed in paragraph (a) of this Rule may be combined in one lantern carried at or near the top of the mast where it can best be seen.

(c)A sailing vessel underway may, in addition to the lights prescribed in paragraph (a) of this Rule, exhibit at or near the top of the mast, where they can best be seen, two all-round lights in a vertical line, the upper being red and the lower green, but these lights shall not be exhibited in conjunction with the combined lantern permitted by paragraph (b) of this Rule. (d)(i) A sailing vessel of less than 7 meters in length shall, if practicable, exhibit the lights prescribed in paragraph (a) or (b) of this Rule, but if she does not, she shall exhibit an all-round white light or have ready at hand an electric torch or lighted lantern showing a white light which shall be exhibited in sufficient time to prevent collision.

(ii)A vessel under oars may exhibit the lights prescribed in this Rule for sailing vessels, but if she does not, she shall exhibit an all-round white light or have ready at hand an electric torch or lighted lantern showing a white light which shall be exhibited in sufficient time to prevent collision.

(e)A vessel proceeding under sail when also being propelled by machinery shall exhibit forward, where it can best be seen, a conical shape, apex downward. A vessel of less than 12 meters in length is not required to exhibit this shape, but may do so.

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.

Exam checkpoints#

1. 1.

   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.

2. 2.

   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.

3. 3.

   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.

4. 4.

   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.

Where Inland differs#

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.

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#

Source links checked against the current public rule corpus on 2026-07-26.

• 33 CFR §83.25 — the section this text comes from, with its neighbours.
• International COLREGs Rule 25 verbatim text is published by the IMO and is authoritative for international waters.

Practice this rule#

One real exam question on this rule, cited to source. No sign-up.