What does «underway» mean?
Not at anchor, not made fast to the shore, not aground. A vessel drifting with her engine stopped is underway too.
Rule 3 (i).
Part of the convention General
The definitions decide who gives way. The commonest confusion is between two similar terms:
- Not under command: through some exceptional circumstance she is unable to manoeuvre as required. This is a breakdown.
- Restricted in ability to manoeuvre: unable to manoeuvre because of the nature of her work. Laying or lifting cable or pipeline, dredging, survey, replenishment underway, launching or recovering aircraft, mine clearance, a tow that severely restricts deviation.
- Constrained by her draught: a power-driven vessel only, whose draught in relation to the available depth and width of navigable water severely restricts her ability to deviate from her course.
- Underway: not at anchor, not made fast to the shore, not aground. Note: underway does not mean moving, a drifting vessel is underway too.
- Engaged in fishing: only when the gear restricts her manoeuvrability. Trolling lines do not count.
- In sight of one another: only when one can be observed visually from the other. A radar contact is not in sight.
- Restricted visibility: fog, mist, falling snow, heavy rainstorms, sandstorms and any similar cause.
At sea it looks like this
A deep-laden tanker in a dredged channel is constrained by her draught, not restricted in ability to manoeuvre. A working dredger is restricted in ability to manoeuvre. A ship with a jammed rudder is not under command. Three different light sets. The first two sit in the give-way order of rule 18, while a vessel constrained by her draught is only one whose safe passage others must avoid impeding.
The rule says«The term „underway“ means that a vessel is not at anchor, or made fast to the shore, or aground.»
Check yourself
When are vessels «in sight of one another»?
Only when one can be observed visually from the other. A radar contact is not in sight, and rules 11 to 18 then do not apply.
Rule 3 (k).
How does «not under command» differ from «restricted in ability to manoeuvre»?
The first cannot manoeuvre through exceptional circumstance (breakdown). The second cannot because of the nature of her work: cable, dredging, replenishment underway, aircraft operations, mine clearance, a heavy tow.
Rule 3 (f), (g).
What is a «vessel constrained by her draught»?
A power-driven vessel only, whose draught in relation to the available depth and width of navigable water severely restricts her ability to deviate from her course.
Rule 3 (h).
Which kind of fishing does not make a vessel «engaged in fishing»?
Fishing with trolling lines or other apparatus that does not restrict manoeuvrability.
Rule 3 (d).
What counts as «restricted visibility»?
Fog, mist, falling snow, heavy rainstorms, sandstorms and any similar cause.
Rule 3 (l).
What is a WIG craft and how does she act?
A multimodal craft that in her main operating mode flies close to the surface using surface-effect action. Taking off, landing and in flight she keeps well clear of all vessels; on the water she is a power-driven vessel.
Rule 3 (m) and 18 (f).