33 CFR § 81.1 - Definitions.
---
identifier: "/us/cfr/t33/s81.1"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "33 CFR § 81.1 - Definitions."
title_number: 33
title_name: "Navigation and Navigable Waters"
section_number: "81.1"
section_name: "Definitions."
chapter_name: "COAST GUARD, DEPARTMENT OF HOMELAND SECURITY"
subchapter_number: "D"
subchapter_name: "INTERNATIONAL NAVIGATION RULES"
part_number: "81"
part_name: "72 COLREGS: IMPLEMENTING RULES"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "33 U.S.C. 1607; E.O. 11964; 49 CFR 1.46."
regulatory_source: "CGD 76-130, 42 FR 17111, Mar. 31, 1977, unless otherwise noted. Redesignated by CGD 81-017, 46 FR 28154, May 26, 1981."
cfr_part: "81"
---
# 81.1 Definitions.
As used in this part:
*72 COLREGS* refers to the International Regulations for Preventing Collisions at Sea, 1972, done at London, October 20, 1972, as rectified by the Proces-Verbal of December 1, 1973, as amended.
*A vessel of special construction or purpose* means a vessel designed or modified to perform a special function and whose arrangement is thereby made relatively inflexible.
*Interference with the special function of the vessel* occurs when installation or use of lights, shapes, or sound-signaling appliances under 72 COLREGS prevents or significantly hinders the operation in which the vessel is usually engaged.
[CGD 77-136, 47 FR 13799, Apr. 1, 1982]