General Definitions — Underway, Power-Driven, and In Sight of One Another

Yes. Underway means not at anchor, not made fast to the shore, and not aground. You are none of those, so you are underway — a state that has nothing to do with whether you are moving .</details>

In sight, and restricted visibility

Vessels are deemed to be in sight of one another only when one can be observed visually from the other . Visual observation is the whole test. A contact held on radar at six miles in dense fog is not in sight.

That definition is a switch. The rules in the section beginning at Rule 11 apply only to vessels in sight of one another COLREGs Rule 11, while the rules in the section beginning at Rule 4 apply in any condition of visibility COLREGs Rule 4. Deciding whether the vessels are in sight decides which body of steering rules is even available to you.

Restricted visibility means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms, or any other similar causes . Darkness appears nowhere in that list.

Length, breadth, and the geographic terms

Length and breadth mean length overall and greatest breadth. Every length threshold in the Rules is measured on that basis, not on registered or waterline length.

The remaining definitions in the Inland rule fix where the Rules apply. Inland Waters means the navigable waters of the United States shoreward of the navigational demarcation lines dividing the high seas from harbors, rivers and other inland waters, together with the waters of the Great Lakes on the United States side of the International Boundary. Western Rivers means the Mississippi, its tributaries, South Pass and Southwest Pass to those same demarcation lines, plus the Port Allen–Morgan City Alternate Route and the Atchafalaya above its junction with that route, including the Old River and the Red River. Great Lakes means the Lakes and their connecting and tributary waters, running as far as the Thomas J. O'Brien Lock on the Calumet River, the east side of the Ashland Avenue Bridge on the Chicago River, and the lower exit of Saint Lambert Lock on the Saint Lawrence. The demarcation line is the trigger in all three: cross it inbound and the Inland Rules govern.

The terms carry across the subchapter. Terms used in the Annex V regulations have the same meanings defined in Part 83 33 CFR §88.03, so a definition learned here is not re-defined elsewhere.

The definitions in Rule 32

Sound signals have their own definitions rule. A short blast is a blast of about one second's duration and a prolonged blast is a blast of from four to six seconds' duration; whistle means any sound signaling appliance capable of producing the prescribed blasts and complying with Annex III COLREGs Rule 32. Four to six seconds is an arbitrary span. It is not derived from anything — commit it.

Telling it apart

One criterion separates the three classes candidates most often swap: what is the source of the restriction on her maneuvering?

• Vessel not under command — an exceptional circumstance has left her unable to maneuver as the Rules require, and therefore unable to keep out of the way 33 CFR §83.03. Something has happened to her that was not planned. Most often misfiled: a vessel with a steering gear casualty gets answered as restricted in her ability to maneuver, because candidates hear "restricted" and stop reading.
• Vessel restricted in her ability to maneuver — the nature of her work restricts her, and she is therefore unable to keep out of the way. Most often misfiled: any tug with a tow. The rule qualifies towing tightly (below).
• Vessel engaged in fishing — fishing with nets, lines, trawls or other fishing apparatus which restricts maneuverability, and expressly not a vessel fishing with trolling lines or other apparatus which do not restrict maneuverability. Most often misfiled: the sportfisherman trolling four rods off the transom. She is fishing in plain English and is a power-driven vessel under the Rules.

The definitions of all three read the same in the International and Inland texts COLREGs Rule 3. Inland §83.03 continues past those paragraphs with the definitions of underway, in sight, restricted visibility, length and breadth, and the geographic terms.

The six named restricted-in-ability operations

The Inland rule states that vessels restricted in their ability to maneuver include, but are not limited to, six operations . The list illustrates the "nature of her work" test rather than exhausting it.

1. Laying, servicing or picking up a navigation mark, submarine cable or pipeline.
2. Dredging, surveying or underwater operations.
3. Replenishment, or transferring persons, provisions or cargo while underway.
4. Launching or recovery of aircraft.
5. Mine clearance operations.
6. A towing operation such as severely restricts the towing vessel and her tow in their ability to deviate from their course.

Item 6 is the one worth reading twice. The qualifier does the work: a towing operation qualifies only where it severely restricts the ability of tug and tow to deviate from their course.