This is an area where all the boats, esp 2 and 3 need to keep abreast of the 'big picture'. If they were as close as that, and in an area where they knew full well there was an obstruction these moves should not come as a surprise and all the boats should be prepared as to how they'll deal...
I think the above assessments are spot on rules-wise, but the situation is pretty easily anticipated.
The problem is that it's the first work after the start, and you want to push to shore as much as possible on that tack because you're fighting the tide up the course. So although it's anticipated, everyone wants to get as close as possible to that side of the course before beating back.
Ah, now we're getting to the fun part. If I'm boat 2 I'm trying to get boat 1 to take my stern after she tacks, then tack on her wind, so I'm pinching up to get separation, even at the loss of a bit of speed, so I don't have to tack when 1 goes. And I'm yelling at boat 3 to get ready to tack as we both need room. So I win if 3 tacks when 1 tacks, then I stand on letting 1 duck me, then I tack on 1's wind and 3 is under my lee. Boy, I miss this stuff. :-)
This is what we originally wanted to go with with (we were boat 2). I should have mentioned that all boats gave plenty of notice of their intention to tack/take water, so lack of warning wasn't an issue. The problem was there was some disagreement between boats on what constituted a reasonable amount of space for 'safe avoidance' after tacking.
Basically, all 3 boats were roughly the same distance apart. It's a one-design class so we're all travelling at roughly the same speed and pointing about the same, so theoretically the conditions are pretty much identical.
We yielded water to 1 (which IMO was the safest decision), but 3 was an arsehole and made us duck. The problem was that they were so close that we barely avoided a collision and basically stalled ourselves in the process.
I contend that it was in no way reasonable to make us avoid them (only some deft piloting from our helmsman and some sharp work on the sheets stopped us having a real disaster). So although there was no collision I don't think that taking their stern was the right option by the rules of racing.
Oh well. Couldn't be arsed protesting so whatever.