COLREGs Rule 31: Lights and shapes for seaplanes and WIG craft

Last reviewed: October 14, 2026

Rule 31 covers seaplanes and WIG craft that cannot show the lights and shapes the Rules prescribe. Where that is impracticable, the craft must show lights and shapes as closely similar in characteristics and position as is possible. The International and Inland texts match except for the reference to "this Part" or "this subpart".

Applies toSeaplanes and WIG craft where it is impracticable to exhibit the prescribed lights and shapes.

What it says

  1. International: A seaplane or WIG craft that cannot practicably exhibit lights and shapes of the prescribed characteristics or in the prescribed positions must exhibit lights and shapes as closely similar as possible in characteristics and position.

    “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 Rules of this Part she shall exhibit lights and shapes as closely similar in characteristics and position as is possible.”

  2. Inland: A seaplane or WIG craft that cannot practicably exhibit lights and shapes of the prescribed characteristics or in the prescribed positions must exhibit lights and shapes as closely similar as possible in characteristics and position.

    “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 Rules of this subpart, she shall exhibit lights and shapes as closely similar in characteristics and position as is possible.”

Common questions

What lights must a seaplane show if it can't use the prescribed ones?

A seaplane must show lights and shapes as closely similar in characteristics and position as is possible. This applies where showing the prescribed ones is impracticable.

“she shall exhibit lights and shapes as closely similar in characteristics and position as is possible.”

Does Rule 31 apply to WIG craft?

Yes. The rule names a seaplane or a WIG craft, and both must follow it where showing the prescribed lights and shapes is impracticable.

“Where it is impracticable for a seaplane or a WIG craft to exhibit lights and shapes of the characteristics or in the positions prescribed”

Is there a difference between the International and Inland versions of Rule 31?

The requirement is the same. The International text refers to the Rules of "this Part" and the Inland text refers to the Rules of "this subpart".

“prescribed in the Rules of this subpart, she shall exhibit lights and shapes as closely similar in characteristics and position as is possible.”

The text of COLREGs Rule 31

U.S. Coast Guard, Navigation Rules and Regulations Handbook

Rule 31: Seaplanes

International (COLREGs)

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 Rules of this Part she shall exhibit lights and shapes as closely similar in characteristics and position as is possible.

Inland Rules

Seaplanes 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 Rules of this subpart, she shall exhibit lights and shapes as closely similar in characteristics and position as is possible.

The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of August 12, 2024. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.