Buoy room rules apply if one of them is in the three boat-length circle, with some exceptions.

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RULE 

Part 2 - When Boats Meet

Section C - At Marks and Obstructions

Rule 18.1 When Rule 18 Applies

Rule 18 applies between boats when they are required to leave a mark on the on the same side and at least one of them is in the zone. However, it does not apply (if) (a), (b), (c), and (d) (do).

Buoy room rules do not apply at a starting mark surrounded by navigable water or at its anchor line from the time boats are approaching them to start until they have passed them...