In the 2008 (and prior) rules, there was a lot of confusion regarding rule 18 (Room at Marks and Obstructions). Most of that stemmed from the fact that when rule 18 conflicted with rules 10-13, then those rules didn't apply. A lot of sailors didn't understand that that right-of-way sometimes changed when boats were about to round or pass a mark.

Starting in 2009, that changed. The new Rule 18 "Mark Room", no longer overrides Part A Rules. Right-of-way doesn't change - instead a boat entitled to mark room can be exonerated for breaking rules 10-13, 15, or 16. "Mark room" has also been explictly defined. I've seen several explanations so far that are based on the former rule 18, not the curret one.

Even so, another look at this scenerio shows that Rule 18 never even comes into play. It really is just a Starboard/Port situation. Rule 10 requires P to keep clear of S. Being outside boat near a mark doesn't change that.

No rule requires S to sail her proper course, so P must be observant of what S does - not what P thinks S should do. If there was thoughtlessness or danger in this scenerio, it is because of P's misunderstanding, not S's.

I hope that helps,
Eric
US SAILING Certified Judge
Member, Area D Appeals Committee