Rule 3-General Definitions explained

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COLREGS-International Regulations for Preventing Collisions at Sea Explained For Exams

Rule 3-General Definitions explained

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Firstly go through the rules, Rule 3 is full of definition; after reading the real definitions as given in the colregs then we will proceed to the explanation-rule 3 general definitions explained.

Rule 3-General Definitions 

For the purpose of these Rules, except where the context otherwise requires:

a) The word vessel includes every description of watercraft, including non-displacement craft, WIG craft and seaplanes, used or capable of being used as a means of transportation on water.

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

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

d) The term vessel engaged in fishing means any vessel fishing with nets, lines, trawls or other fishing apparatus which restrict manoeuvrability but does not include a vessel fishing with trolling lines or other fishing apparatus which do not restrict manoeuvrability.

e) The word seaplane includes any aircraft designed to manoeuvre on the water.

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

g) The term vessel restricted in her ability to manoeuvre means a vessel which from the nature of her work is restricted in her ability to manoeuvre 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 manoeuvre shall include but not be limited to:

1. a vessel engaged in laying, servicing or picking up a navigation mark, submarine cable or pipeline;

2.a vessel engaged in dredging, surveying or underwater operations;

3.a vessel engaged in replenishment or transferring persons, provisions or cargo while underway;

4. a vessel engaged in the launching or recovery of aircraft;

5. a vessel engaged in mine clearance operations;

6. 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.

h) The term vessel constrained by her draught means a power-driven vessel which because of her draught 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.

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

j) The words length and breadth of a vessel mean her length overall and greatest breadth.

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

l) 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.

m)The term Wing-In-Ground (WIG) craft means a multimodal craft which, in its main operational mode, flies in close proximity to the surface by utilizing surface-effect.

Explanation of Rules

Tips: We sorted important topics below, it will help you out in exams. good luck


a) explanation of Rule 3 a

  • All types of craft that float on water and are used as a means of transportation. Also included all crafts which do not displace water – such as hovercraft. Images of hovercraft given below.
  • A seaplane when on the water displaces water so as long as it is on the surface of the water it is considered as a vessel. All barges are also included Since no propulsion system has been mentioned in this part of the Rule.

b) explanation of Rule 3 b

  • Power here means power obtained from machinery, such as diesel engines, from the smallest to the largest.
  • sailing vessels are not included as long as they are purely under sail.
  • vessels under oars are also not included.

c) explanation of Rule 3 c

  • Sailing vessels of today rely on some form of machinery propulsion, that is when the wind is calm and the sailing vessel is not moving.
  • The sailing vessels (some of them) have provision for use of their main engine and propeller.
  • So as long as this main engine on sailing vessels is not used they are termed as sailing vessels, the moment their main engine is started they are termed as power-driven vessels, even if they hoist sails.

d) explanation of Rule 3 d

  • Fishing vessels means vessels actually fishing and which due to their equipment in the water are unable to move away and keep clear of other vessels.
  • If the fishing vessel is not fishing or is using equipment, which does not restrict their taking evasive, action for safety then they are not termed as fishing vessels.
  • The equipment as specified under the Rules is nets, lines (longline tuna fishing), trawls or other equipment, which are similar.
  • Below images are related to fishing vessels. Go through it and understand different types of vessels,

e) explanation of Rule 3 e

  • Obvious meaning, an aircraft which is in an emergency is landing (ditching) in the water would not be termed as a seaplane, only those planes which by their construction and purpose can safely land, take-off and manoeuvre to a pier or jetty are called seaplanes.
  • Images of seaplanes are given below,

f) explanation of Rule 3 f

  • Here a vessel not under command means any vessel, which because of some reason cannot keep out of the way of other vessels. Like breakdown and she cannot anchor, steering failure, launching a rescue boat or a lifeboat.

g) explanation of Rule 3 g

  • This includes a ship that is doing some special work by which she can move only in one direction- say ahead, but cannot alter her course to take evasive action neither can she slow down nor speed up to avoid a collision then, in that case, the vessel would be restricted in her ability to manoeuvre.

h) explanation of Rule 3 h

  • This is applicable to POWER-DRIVEN VESSELS, which because of their draft in comparison to the depth of water at that place is so great that she cannot alter to avoid a collision since to do that they would run aground.
  • the vessel would not be classified as constrained by her draught if there were an adequate width of the channel through which they are moving.

i) explanation of Rule 3 i

  • The word underway means that a vessel is not at anchor, or made fast to the shore. or aground.

j) explanation of Rule 3 j

  •  The words length and breadth of a vessel mean her length overall and greatest breadth.

k) explanation of Rule 3 k

  • The vessel being observed should be capable of being seen with the observer’s eyes and not by any electronic device, this is so because the aspect of the vessel is very important.
  • the human brain analyses data from input more effectively than an electronic device. A change in other vessels heading is very readily apparent when observing visually, by electronic means it has a time lag.

l) explanation of Rule 3 l

  • Conditions mentioned in the rules also by any other means may cause restricted visibility.

m) explanation of Rule 3 m

  • A ground-effect vehicle also called a wing-in-ground

That’s all for today, study and understand the rules. if you still have any doubts about this topic come in the comment section,

learn more about ror explanation for various rules.

Thank you,

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3 thoughts on “Rule 3-General Definitions explained”

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