COLREGs · Rule 31 · 33 CFR §83.31
Seaplanes
Seaplanes (and WIG craft) exhibit lights and shapes characteristic of vessels of their category as far as practicable.
What does Rule 31 actually say?#
Source
Practice this rule#
One real exam question on this rule, cited to source. No sign-up.
Under the International Rules, a vessel constrained by her draft underway in restricted visibility shall sound ______.
Does Inland Rule 31 change anything?#
Inland Rule 31 is 33 CFR §83.31, reproduced above, and carries no exam-relevant divergence from COLREGs Rule 31. One answer serves both the International and the Inland version of a Rules of the Road question on this rule — which is worth knowing precisely because several neighbouring rules do not work that way.
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#
Rule 31 is a single sentence and the exam value is the standard it sets: a seaplane or WIG craft that cannot show the prescribed lights and shapes is not excused, it must show the closest thing it can.
What does the exam actually test here?#
Who it covers
Seaplanes and WIG craft
The rule applies where it is impracticable for a seaplane or a WIG craft to exhibit lights and shapes of the characteristics, or in the positions, prescribed in the lights-and-shapes rules.
The standard
As closely similar as possible
She shall exhibit lights and shapes as closely similar in characteristics and position as is possible. Impracticability reduces the requirement; it does not remove it.
Conduct is separate
Rule 18 still applies
Rule 31 is only about lights and shapes. A seaplane on the water still keeps well clear of all vessels under Rule 18(e), and complies with Rules 4–19 where risk of collision exists.
Rule 31 — common exam questions#
What does Rule 31 require of a seaplane?
Where it is impracticable for a seaplane or WIG craft to exhibit lights and shapes of the prescribed characteristics or in the prescribed positions, she shall exhibit lights and shapes as closely similar in characteristics and position as is possible (33 CFR §83.31).
Is a seaplane exempt from showing lights?
No. Rule 31 lowers the standard to the closest possible approximation where full compliance is impracticable, but it does not exempt a seaplane from showing lights and shapes.
How does a seaplane fit into the steering rules?
Under Rule 18(e) a seaplane on the water shall in general keep well clear of all vessels and avoid impeding their navigation, but where risk of collision exists she complies with Rules 4 through 19 like any other vessel.
Authoritative source#
- 33 CFR §83.31 — this section with its neighbours. 33 CFR Part 83 is public domain; checked 2026-05-16.
- COLREGs Rule 31 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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