COLREGS Rule 3 — General Definitions

Rule Text

What it means on the water

• →Sailing vessel using engine = power-driven vessel (must show cone by day).
• →Vessel engaged in fishing means gear that restricts maneuverability — trolling lines do NOT qualify.
• →NUC: vessel unable to maneuver due to an exceptional circumstance (breakdown, casualty).
• →RAM: vessel restricted by the nature of its work (dredging, cable laying, minesweeping, replenishment at sea, etc.).
• →Constrained by Draft (CBD): applies only to power-driven vessels; COLREGS only — not in Inland Rules.
• →Underway means not at anchor, made fast to shore, or aground — the vessel need not be moving.
• →Making way means the vessel is actually moving through the water, as opposed to merely drifting.

Common exam mistakes

• ✗Saying a vessel trolling for fish is 'engaged in fishing' under Rule 3 — trolling lines do not restrict maneuverability.
• ✗Confusing NUC (breakdown/casualty) with RAM (restricted by work type).
• ✗Thinking a sailing vessel using its engine is still a sailing vessel — it is a power-driven vessel.
• ✗Applying CBD status to sailing vessels — CBD is power-driven only under COLREGS.
• ✗Confusing 'underway' (not anchored/moored/aground) with 'making way' (actually moving through water).

USCG exam questions — Rule 3

These questions are drawn from the same pool used in real USCG licensing exams. Correct answers and explanations are shown.

1. 1. 72 COLREGS apply to vessels upon which waters?

   • A.All vessels on the high seas and connected navigable waters✓
   • B.Only vessels on the high seas beyond 12 nautical miles
   • C.Only vessels in international waters beyond 3 nautical miles
   • D.All vessels on the high seas and in U.S. inland waters

   Why: Rule 1(a) states the rules apply on the high seas and in all waters connected therewith navigable by seagoing vessels. This broad application covers coastal, port, and offshore waters unless a nation has established special inland rules for specific waters.

2. 2. Under 72 COLREGS, a 'power-driven vessel' is defined as:

   • A.Any vessel propelled by machinery✓
   • B.Any vessel over 20 meters propelled by an engine
   • C.A vessel propelled by machinery and not also under sail
   • D.A vessel whose primary means of propulsion is an internal combustion engine

   Why: Rule 3(b) defines a power-driven vessel simply as any vessel propelled by machinery. There is no size qualifier. Critically, a sailing vessel that is also using its engine is considered a power-driven vessel under Rule 25(e).

3. 3. Which of the following is NOT included in the definition of 'restricted visibility' under 72 COLREGS?

   • A.Fog
   • B.Heavy rain
   • C.Darkness✓
   • D.Sand storm

   Why: Rule 3(l) defines restricted visibility as any condition where visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms, or any other similar causes. Darkness is not restricted visibility — vessels at night use the same steering and sailing rules as daytime, not the Rule 19 restricted visibility rules.

4. 4. Under COLREGS Rule 3(a), the term 'vessel' includes:

   • A.Every description of water craft, including non-displacement craft, WIG craft, and seaplanes, used or capable of being used as a means of transportation on water✓
   • B.Only self-propelled watercraft of more than 7 meters in length
   • C.All watercraft except non-displacement craft such as hovercraft and hydrofoils
   • D.Motorized vessels only; sailing vessels are covered under a separate definition

   Why: Rule 3(a) defines 'vessel' very broadly to include every description of water craft including non-displacement craft, WIG craft, and seaplanes, covering essentially any craft used or capable of being used for transportation on water.

5. 5. Under COLREGS Rule 3(g), which vessel qualifies as restricted in her ability to maneuver?

   • A.A vessel engaged in dredging, surveying, or underwater operations✓
   • B.A vessel with a temporary engine malfunction causing reduced speed
   • C.A vessel waiting at anchor for a berth to become available
   • D.A vessel towing astern with a tow less than 25 meters in length

   Why: Rule 3(g) explicitly includes vessels engaged in dredging, surveying, or underwater operations among RAM vessels, because these activities physically restrict the vessel's ability to deviate from her course.

6. 6. A vessel that is adrift with her engines stopped and is not at anchor is considered to be:

   • A.Underway but not making way✓
   • B.Not underway, because she has no steerage way
   • C.At anchor by constructive definition
   • D.Underway and making way if she is moving due to current

   Why: Under Rule 3(i), a vessel is underway if she is not anchored, made fast to shore, or aground. She need not be making way; a drifting vessel is underway but not making way, and her lights must reflect this status.

7. 7. Under Rule 3(d), which vessel qualifies as 'engaged in fishing' for the purpose of the navigation rules?

   • A.A vessel fishing with nets, lines, trawls, or other fishing apparatus which restricts maneuverability✓
   • B.Any vessel with fishing gear aboard that is actively fishing
   • C.A vessel trawling or using nets, regardless of whether maneuverability is restricted
   • D.A vessel fishing with any apparatus from a fixed position or at anchor

   Why: Rule 3(d) defines a vessel engaged in fishing as one using nets, lines, trawls, or other apparatus that restricts maneuverability — the restriction of maneuverability is the key qualifier; a vessel trolling with lines that do not restrict her is NOT 'engaged in fishing' under the rules.

8. 8. Which situation would most likely qualify a vessel as 'not under command' under Rule 3(f)?

   • A.Complete loss of steering due to a rudder casualty in heavy weather✓
   • B.Reduced speed due to fouled propeller requiring diver inspection
   • C.Maneuvering restrictions caused by towing a barge astern
   • D.Inability to alter course due to a narrow channel

   Why: NUC status requires an 'exceptional circumstance' rendering the vessel unable to maneuver as required — a complete loss of steering from a rudder casualty is the classic example of such an exceptional circumstance, distinct from operational or navigational restrictions.

Frequently asked questions

What is the difference between a vessel not under command and a vessel restricted in ability to maneuver?

A NUC vessel is unable to maneuver due to an exceptional circumstance such as mechanical failure or casualty — something unplanned. A RAM vessel is restricted by the nature of its work — an expected operational constraint such as dredging, cable laying, or minesweeping. Both display special lights, but the cause and planning are different.

Is a boat trolling for fish considered a 'vessel engaged in fishing' under COLREGS?

No. Rule 3 defines a vessel engaged in fishing as one using nets, lines, trawls, or other gear that restricts its maneuverability. Trolling lines do not restrict maneuverability, so a trolling vessel has no special status and must follow the normal steering and sailing rules.

What does 'underway' mean in the Rules?

Underway means a vessel is not at anchor, made fast to the shore, or aground. An underway vessel may or may not be moving through the water. A vessel that is underway but not propelling itself (drifting) is underway but not making way.

All COLREGS rules