Part A — General

COLREGs Rule 3: General definitions

Rule 3 defines the words the rest of the rules depend on: vessel, power-driven, sailing vessel, fishing, not under command, restricted in ability to manoeuvre, constrained by draught, underway, in sight and restricted visibility.

What Rule 3 says

  1. A vessel is any watercraft used or able to be used as a means of transport on water, including non-displacement craft, wing-in-ground (WIG) craft and seaplanes.
  2. A power-driven vessel is any vessel propelled by machinery. A sailing vessel is any vessel under sail, provided its engine, if fitted, is not being used.
  3. A vessel engaged in fishing is one fishing with nets, lines, trawls or other gear that restrict its manoeuvrability. Trolling lines do not count.
  4. A vessel not under command (NUC) is one that, through some exceptional circumstance such as a steering failure, cannot manoeuvre as the rules require.
  5. A vessel restricted in her ability to manoeuvre (RAM) is one whose work limits its ability to get out of the way: laying buoys or cables, dredging, surveying, diving operations, replenishing at sea, launching or recovering aircraft, mine clearance, or a tow that restricts its course.
  6. A vessel constrained by her draught (CBD) is a power-driven vessel severely restricted in its ability to deviate from its course by the available depth and width of water.
  7. Underway means not at anchor, not made fast to the shore and not aground. Vessels are in sight of one another only when one can be seen visually from the other.
  8. Restricted visibility is any condition where visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or similar causes.

This is a plain-English summary, not the official wording. For the exact text, see the IMO convention. In UK waters the rules are given legal force by the Merchant Shipping (Distress Signals and Prevention of Collisions) Regulations.

What it means on a yacht

The moment your engine is running and in gear, your yacht is a power-driven vessel, even with sails up. Drifting with the engine off and no anchor down, you are still underway.

Practise it

Test yourself on who gives way in the free COLREGs trainer, or print the rules of the road cheat sheets for the chart table.

Other rules in Part A

Frequently asked questions

Is a sailing boat with its engine on a sailing vessel?

No. Under Rule 3 a sailing vessel using its engine is a power-driven vessel, and must follow the rules (and show the day shape) for one.

What is the difference between underway and making way?

Underway means not anchored, moored or aground. Making way means actually moving through the water. A drifting yacht is underway but not making way.