Rule 25 — Lights for Sailing Vessels and Vessels Under Oars

What the rule requires

A sailing vessel underway exhibits sidelights and a sternlight 33 CFR §83.25. Two lights. The rule prescribes those and stops there, and the International text is word-for-word the same on this point COLREGs Rule 25. A question that offers you a sailing vessel showing a masthead light as her ordinary display under sail alone is offering you something Rule 25 does not prescribe.

The combined lantern: under 20 meters

In a sailing vessel of less than 20 meters in length, 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 COLREGs Rule 25(b). Identical under Inland.

Two things about that. It is permissive — a 15-meter sloop showing separate sidelights and a separate sternlight is correct, and so is the same sloop showing the combined lantern. And 20 meters is an arbitrary line drawn by the drafters; there is nothing to derive, so commit the number. At 20 meters and above, the combining option is gone.

The lantern carries the paragraph (a) lights and nothing else. Its position at the top of the mast does not make it, or add, a masthead light.

Red over green: optional, additional, and exclusive

A sailing vessel underway may, in addition to her sidelights and sternlight, exhibit at or near the top of the mast two all-round lights in a vertical line, the upper red and the lower green. She may not exhibit them in conjunction with the combined lantern permitted by paragraph (b) COLREGs Rule 25(c). Same under Inland.

The common mnemonic is "red over green, sailing machine." Use it — it is what your fellow candidates learned and what the fleet says. It carries the colour order and nothing else, so three corrections ride with it: the pair is optional, not required; it is additional to the sidelights and sternlight, which are still shown; and it is barred whenever the combined lantern is in use. There is no length qualifier on red over green. A 40-meter schooner may show it; so may a 9-meter sloop, provided she is not using the combined lantern.

A 15-meter sloop under sail alone at night has her combined lantern lit at the top of the mast and wants to add red over green above it. Permitted?

No. Rule 25(c) forbids exhibiting the two all-round lights in conjunction with the combined lantern permitted by 25(b). She may have one arrangement or the other: combined lantern alone, or separate sidelights and sternlight with red over green above. Both International and Inland.

Sail plus machinery: the cone, and where the two regimes split

A vessel proceeding under sail when also being propelled by machinery exhibits forward, where it can best be seen, a conical shape, apex downward COLREGs Rule 25(e). The trigger is machinery propelling her while sail is set, not the sail alone and not the engine idling in neutral.

This is the divergence on Rule 25, and it is worth more marks than anything else in the rule:

• International — the cone is required, at any length. The text carries no exemption.
• Inland — a vessel of less than 12 meters in length is not required to exhibit the shape, but may do so .

Twelve meters, Inland only. The exam labels these questions, so read the label before you reach for the exemption.

Rule 25 governs the dayshape for the motorsailing vessel. What she shows for lights in that condition is a power-driven vessel question and belongs to Rule 23, not here.

Under 7 meters, and vessels under oars

A sailing vessel of less than 7 meters shall, if practicable, exhibit the lights prescribed in paragraph (a) or (b). If she does not, the fallback applies: a white light shown in sufficient time to prevent collision COLREGs Rule 25(d).

The wording of that fallback is where the two texts part company. The International text names an electric torch or lighted lantern showing a white light, kept ready at hand and exhibited in sufficient time to prevent collision. The Inland text permits either an all-round white light or the torch or lighted lantern ready at hand . On an exam question phrased loosely — "shall show a white light in sufficient time to prevent collision" — that answer is correct under both.

A vessel under oars may exhibit the lights prescribed for sailing vessels; if she does not, she has the same white-light fallback. There is no length threshold on the oars branch of the rule. The 7-meter figure belongs to the sailing vessel only, and a rowed vessel of any size may fall back to the white light.

How far these lights must show

The minimum ranges are set by Rule 22. The chunks supplied here are the International text, which flags that Inland Rule 22 differs, so do not carry these figures onto an "(Inland Only)" question COLREGs Rule 22.

For the lights Rule 25 actually prescribes:

• Less than 12 meters — sidelight 1 mile; sternlight 2 miles; all-round light 2 miles COLREGs Rule 22(c).
• 12 meters or more but less than 50 meters — sidelight 2 miles; sternlight 2 miles; all-round light 2 miles COLREGs Rule 22(b).
• 50 meters or more — sidelight 3 miles; sternlight 3 miles; all-round light 3 miles.

The sidelight is the only one of the three that changes at 12 meters. A 10-meter sailing vessel's sternlight is still a 2-mile light while her sidelights are 1-mile lights, and candidates routinely answer 2 miles for both.

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Telling it apart

The four displays in this rule are separated by one question: what does the display do to the sidelights and sternlight?

• Combined lantern, 25(b) — replaces them, in one fitting at or near the top of the mast. Available only below 20 meters. Bars red over green.
• Red over green all-round pair, 25(c) — adds to them. No length limit, and the sidelights and sternlight stay lit. Misfiled as a substitute display, which is the single most productive wrong answer in this rule.
• White light, 25(d) — stands in for the whole display, but only for a sailing vessel under 7 meters, or a vessel under oars, that is not showing the prescribed lights.
• Cone, apex downward, 25(e) — a dayshape, and the only item here triggered by propulsion rather than by choice.

Working a question

0930. A 10-meter sloop is transiting Inland waters with main and jib set and the diesel engaged at 1400 rpm. The question is labelled "(Inland Only)" and asks what she is required to exhibit forward.

1. Is she under sail? Yes — canvas set and drawing. Rule 25 is in play rather than Rule 23 alone.
2. Is machinery propelling her? Yes. That engages 25(e), the conical shape apex downward. Had the engine been in neutral, 25(e) would not apply and she would be a sailing vessel showing only her 25(a) lights by night, no shape by day.
3. Which regime does the question label? Inland. So the length exemption is live and must be checked.
4. What is her length? 10 meters, which is less than 12. Under Inland she is not required to exhibit the cone, though she may.
5. Select the option that says the shape is not required. An option reading "must exhibit a black conical shape, apex downward" is the trap, and it is the correct answer to the same question labelled "(International Only)" — where no length exemption exists.

Step 3 is the one candidates skip. The label on the question is data, not decoration.

Same sloop, same morning, but she is 30 miles offshore on the high seas. What changes?

The cone becomes mandatory. The International text requires the conical shape apex downward of any vessel proceeding under sail while also propelled by machinery, with no exemption by length. Nothing about her lights changes — the shape is the whole of the difference.

Where candidates lose the point

Combining the two masthead options. The candidate reasons that the combined lantern is permitted and red over green is permitted, so both together must be permitted. Rule 25(c) forbids exactly that pairing by name. This is tested more often than anything else in the rule.

Treating red over green as the sailing vessel's whole display. "Red over green, sailing machine" invites the reader to picture two lights and stop. The rule grants them in addition to the sidelights and sternlight, so an answer stating that a vessel showing red over green need not show sidelights is wrong.

Applying the 12-meter exemption to an International question. The exemption for vessels under 12 meters is Inland. Under International the shape is required at any length, and a candidate who has drilled the Inland text will confidently pick "not required."

Importing 20 meters into paragraph (c). The 20-meter threshold governs the combined lantern only. Answering that only vessels under 20 meters may show red over green attaches a limit the rule does not contain.

Putting a 7-meter cap on the vessel under oars. The 7-meter figure qualifies the sailing vessel in 25(d)(i). The oars provision has no length in it at all.

Answering 2 miles for a small sailing vessel's sidelights. Under 12 meters the sidelight range drops to 1 mile while the sternlight stays at 2 — an asymmetry the eye slides over when the numbers are read down a column.

Check yourself

(Both International & Inland) You sight a vessel showing sidelights, a sternlight, and two all-round lights in a vertical line at the top of her mast, red above green. What is she, and what does the display tell you about her length?

A sailing vessel underway, exhibiting the optional lights of Rule 25(c). The display tells you nothing about her length — there is no length restriction on red over green. It does tell you she is not using the combined lantern of 25(b), since the two arrangements may not be shown together.

(Inland Only) A 9-meter sailing vessel is motorsailing at midday on inland waters and exhibits no shape forward. Is she in compliance?

Yes. Under Inland, a vessel of less than 12 meters proceeding under sail while also propelled by machinery is not required to exhibit the conical shape, though she may.

(International Only) Same 9-meter vessel, same condition, on the high seas. Is she in compliance with no shape forward?

No. The International rule requires the conical shape, apex downward, exhibited forward where it can best be seen, of any vessel proceeding under sail while also being propelled by machinery. No length exemption applies.

(Both International & Inland) A 22-meter sailing yacht wants to fit a single combined lantern at her masthead in place of sidelights and a sternlight. Permitted?

No. The combining option in 25(b) is limited to sailing vessels of less than 20 meters in length. She shows sidelights and a sternlight, and she may add red over green above them if she chooses.

(Both International & Inland) A rowboat underway at night carries no fitted navigation lights. What is required of her?

A white light, exhibited in sufficient time to prevent collision. A vessel under oars may show the lights prescribed for sailing vessels; if she does not, she falls back to the white light — under International an electric torch or lighted lantern ready at hand, and under Inland either that or an all-round white light. No length limit applies to the oars provision.

(International Only) What minimum visibility must the sidelights and sternlight of a 10-meter sailing vessel have?

Sidelights 1 mile, sternlight 2 miles. Vessels of less than 12 meters get the reduced 1-mile sidelight; the sternlight and any all-round light remain 2-mile lights. Inland Rule 22 is a separate text and these figures should not be carried to an Inland-labelled question.

(Both International & Inland) Under sail with the engine running in neutral to charge batteries, is the conical shape required by day?

No. The trigger in 25(e) is a vessel proceeding under sail when also being propelled by machinery. Machinery running without propelling her does not engage the rule.