To help clarify some of what's been discussed in this thread, I thought I'd post the General Definitions from the COLREGS (Rules of the Road).

[color:"green"]For the purpose of these Rules, except where the context otherwise requires:

(3a) The word "vessel" includes every description of water craft, including nondisplacement craft and seaplanes, used or capable of being used as a means of transportation on water.

(3b) The term "power-driven vessel" means any vessel propelled by machinery.

(3c) The term "sailing vessel" means any vessel under sail provided that propelling machinery, if fitted, is not being used.

(3d) The term "vessel engaged in fishing" means any vessel fishing with nets, lines, trawls or other fishing apparatus which restrict maneuverability, but does not include a vessel fishing with trolling lines or other fishing apparatus which do not restrict maneuverability. See Note on fishing vessel terminology.

(3e) The word "seaplane" includes any aircraft designed to maneuver on the water.

(3f) The term "vessel not under command" means a vessel which through some exceptional circumstance is unable to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel.

(3g) The term "vessel restricted in her ability to maneuver" means a vessel which from the nature of her work is restricted in her ability to maneuver as required by these Rules and is therefore unable to keep out of the way of another vessel.

The term 'vessels restricted in their ability to maneuver' shall include but not be limited to:


(i) a vessel engaged in laying, servicing or picking up a navigation mark, submarine cable or pipeline;
(ii) a vessel engaged in dredging, surveying or underwater operations;
(iii) a vessel engaged in replenishment or transferring persons, provisions or cargo while underway;
(iv) a vessel engaged in launching or recovery of aircraft;
(v) a vessel engaged in mine clearance operations;
(vi) a vessel engaged in a towing operation such as severely restricts the towing vessel and her tow in their ability to deviate from their course;

(3h) The term "vessel constrained by her draft" means a power-driven vessel which, because of her draft in relation to the available depth and width of navigable water is severely restricted in her ability to deviate from the course she is following. See note on Inland definitions.

(3i) The word "underway" means a vessel that is not at anchor, or made fast to shore, or aground.

(3j) The words "length" and "breadth" of a vessel means her length overall and greatest breadth.

(3k) Vessels shall be deemed to be in sight of one another only when one can be observed visually from the other.

(3l) The term "restricted visibility" means any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or any other similar causes.[/color]