IALACOLREG
Academy

COLREG

Rule 11: Application

COLREG reserves the rules in this section for vessels in sight of one another.

Rule 11 of 41

Decide

Do the Section II rules (vessels in sight of one another) apply?

Tap a card and then its group, or drag it.

The rule in plain words

  1. When does Section II apply?Rules 12 to 18 of COLREG apply only when the vessels are in sight of one another: it is enough that one can see the other by eye.
  2. What does in sight mean?Check Rule 3(k): you must be able to see the other vessel; radar-only contact does not meet the visual condition.
  3. What if they are not in sight?If vessels are not in sight in or near restricted visibility, don't use this section: consult Rule 19.
Two vessels in clear daylight, each plainly visible from the other: Section II (Rules 12–18) applies only to vessels in sight of one another.

Before you read on: what would you do?

Question 1/1

When do the rules in Section II apply?

Frequent mistakes

  • Wrong: "Radar contact means we are in sight."

    Right: Radar does not replace the visual contact required by Rule 11.

  • Wrong: "Section II applies even when you cannot see the other vessel."

    Right: It applies only to vessels in sight of one another.

  • Wrong: "Rule 11 and Rule 19 are the same thing."

    Right: For vessels not in sight in restricted visibility, consult Rule 19.

Exam keys & interpretation

  1. "Only" is decisive: if neither vessel can see the other, do not choose the rules in this section.
  2. Radar without sighting: the question tests Rule 11's scope, not a manoeuvre.
  3. In or near restricted visibility + not in sight → look for Rule 19.

How to read it

Read "in sight" literally: one must be able to observe the other visually; electronic detection is not enough.

Separate the situations: if one sees the other, this section; no sight in restricted visibility, Rule 19.

Key points

  • Section II → visual encounter, not abstract detection.
  • Rules 12–18: only within this situation.
  • Radar alone: does not activate this section.
  • Restricted visibility without sighting → check Rule 19.

Test your knowledge

3 questions to check it. Pick an answer to see why.

Question 1/3

Two vessels have radar contact only. What does Rule 11 indicate?

Now put it into practice40 questions with explained answers · no sign-up
Practise with the free test Follow the path through all 41 rules in the Academy. The first units are free.

Official text

IMO COLREG 1972 U.S. Coast Guard — International Navigation Rules (2024)

Full wording of the rule, reproduced from the official source below.

Rules in this section apply to vessels in sight of one another.
Source:

More rules in this Part

More resources

Reviewed by Ramon Curto, Nautical teacher at IECNPC · Last reviewed:

Frequently asked questions about COLREG Rule 11

Which COLREG rules apply only to vessels in sight of one another?

Rules 11 to 18, the Section II rules. Rule 11 states that this Section applies only to vessels in sight of one another.

Does radar contact mean two vessels are in sight of one another?

No. Two vessels are in sight only when one can be observed visually from the other, so radar observation alone does not count. Applying the crossing or overtaking rules to a contact detected only on radar is a common mistake.

Which rule applies when vessels cannot see each other?

In restricted visibility, Section III — Rule 19 — applies instead of the Section II steering rules.