Explanation of Rule 18 Responsibilities Between Vessels. Rule 18 follows Explanation

Vessels constrained by their draught.
Any vessel, except a vessel not under command or restricted in her ability to manoeuvre, must avoid impeding the safe passage of a vessel constrained by her draught and exhibiting the signals mentioned in Rule 28. The words ‘if the circumstances of the case admit’ are included in Rule 18(d) to take account of the fact that some vessels, particularly vessels engaged in fishing, may be unable to take effective avoiding action in sufficient time. A vessel required to avoid impeding the safe passage of a vessel constrained by her draught must, if the circumstances of the case admit, take early action to allow sufficient sea room for the safe passage of the other vessel. Rule 18(d)(ii) requires a vessel constrained by her draught to navigate with particular caution having full regard to her special condition.

Categories of vessels.
A vessel may only be justified in regarding herself as falling within a certain category of privileged vessels for the purpose of Rule 18 if she satisfies the conditions of the relevant definition of Rule 3 and is also showing the lights or shapes prescribed in the appropriate Rule of Part C. A vessel engaged in a towing operation is not privileged with respect to other vessels unless she is severely restricted in her ability to deviate from her course.

Action to be taken when Rule 18 applies A vessel required to keep out of the way by this Rule must take early and substantial action in accordance with Rule 16. The privileged vessel is required to keep her course and speed in accordance with Rule 17(a)(i), so far as she is able to do so. The give- way vessel must take into account the possibility that the nature of the work being carried out, or the special circumstances which apply, may make it impossible for the stand-on vessel to keep both course and speed.

A seaplane on the water shall, in general, keep well clear of all vessels and avoid impeding their navigation. In circumstances, however, where risk of collision exists, she shall comply with the Rules of this part.
A WIG craft, when taking off, landing and in flight near the surface, shall keep well clear of all other vessels and avoid impeding their navigation.
A WIG craft operating on the water surface shall comply with the Rules of this part as a power driven vessel.

RULE 18
Responsibilities Between Vessels.
Except where Rules 9, 10, and 13 otherwise require:
(a) A power-driven vessel underway shall keep out of the way of:
(i) a vessel not under command;
(ii) a vessel restricted in her ability to manoeuvre;
(iii) a vessel engaged in fishing;
(iv) a sailing vessel.

(b) A sailing vessel underway shall keep out of the way of:
(i) a vessel not under command;
(ii) a vessel restricted in her ability to manoeuvre;
(iii) a vessel engaged in fishing.

(c) A vessel engaged in fishing when underway shall, so far as possible, keep out of the way of:
(i) a vessel not under command;
(ii) a vessel restricted in her ability to manoeuvre.

(d) (i) Any vessel other than a vessel not under command or a vessel restricted in her ability to manoeuvre shall, if the circumstances of the case admit, avoid impeding the safe passage of a vessel constrained by her draught, exhibiting the signals in Rule 28.
(ii) A vessel constrained by her draught shall navigate with particular caution having full regard to her special condition.
(e) A seaplane on the water shall, in general, keep well clear of all vessels and avoid impeding their navigation. In circumstances, however, where risk of collision exists, she shall comply with the Rules of this part.
(f) (i) A WIG craft, when taking off, landing and in flight near the surface, shall keep well clear of all other vessels and avoid impeding their navigation.
(ii) A WIG craft operating on the water surface shall comply with the Rules of this part as a power driven vessel.