Clear ahead at the zone

The situation

Running down to the leeward mark, Green is clear ahead of Blue as the first of them reaches the three-length zone. Blue then lunges for the inside at the last second.

The question

Who is entitled to room, and does Blue's late inside dive earn anything?

The ruling

Green is entitled. When the boats are not overlapped as the first of them reaches the zone, the boat that hasn't reached the zone — the one clear astern — must give the other mark-room (rule 18.2(a)(2)); mark-room isn't only for an inside overlap. Blue can't manufacture an inside overlap inside the zone and demand room; she keeps clear and rounds behind. Watch the animation: Green takes her room and Blue's late dive gets nothing.