At position 2, Blue is clear ahead of both Yellow and Green and is an obstruction to both.  Green has right of way over Yellow, but must give Yellow room to keep clear of Blue and pass the shallow water obstruction.  At position 3, all three boats are overlapped and, as windward boat, Blue must keep clear of Yellow and Yellow must keep clear of Green.  Blue is entitled to room at the obstruction (shallow water) and Green must give both Blue and Yellow room to pass that obstruction.
See rule 19.2(a) and (b)
See also Case 41
https://www.sailing.org/tools/documents/WSCaseBook20212024-[26935].pdf

Firstly if a boat calls for water RRS 20 you must give her water. In this instance Yellow did not fulfill any of the conditions necessary to enable her to ask for room or water. She was not close hailed nor was she approaching an obstruction. 
So your recourse was to give her room and then protest her for breaking RRS20.
Yellow had 3 rules to contend with,
14 avoiding contact 
12 being clear astern of Blue 
11 being windward to you Green. 
She avoided Blue and therefore did not break RRS 14 or 12. 
However she did not keep clear of Green and broke 11 Windward Leeward. 
And of course RRS 20. 
Because she was in danger of running into Blue was of her own doing and she should have slowed down to avoid that situation. 
The shallow water was IMHO a continuous obstruction and Yellow was entitled to room which I believe you gave her. I make all these comments in the beliefs that your diagram was not meant to indicate that there was contact at positions 1, 2 & 3
Hope this helps. 

This is actually a pretty tough question because it has to do with the problem of the "disappearing obstruction".  

Here's why it's called that:  At positions 1 and 2, Blue is clear ahead of both Green and Yellow, so she's an obstruction to both of them, and because she's a boat racing, she isn't a continuing obstruction.  Green is about to pass Blue to leeward, so Yellow is entitled, under rule 19, to pass Blue on the same side.  So yes, at that point it seems as if Yellow will be entitled to room to pass Blue, under rule 19.  But as soon as either Green or Yellow becomes overlapped to leeward of Blue, Blue ceases to be an obstruction to that boat -- poof! -- and therefore rule 19 no longer applies to Yellow and Green.  

In position 3, Yellow is overlapped to leeward of Blue, so Blue must keep clear.   Because the overlap was caused by Yellow's action, Yellow must initially give Blue room to keep clear, and it looks as if there's not much place for Blue to go (though if the shallow water is shown by the line, she could certainly move over a half boatlength or so).  Yellow  must also keep clear of Green because Green is on the same tack and overlapped to leeward of Yellow.  

So my call is:  Yellow breaks rule 11 with respect to Green.  Green does not owe Yellow room under any rule.  Yellow and Blue are overlapped on the same tack, so Blue must keep clear of Yellow if she can.  So the whole issue comes down to whether,between positions 2 and 3, Blue could have kept clear of Yellow in a seamanlike manner.  If the answer is no, then Blue is exonerated for breaking rule 11 (Windward/Leeward).  If the answer is yes, i.e, Blue could have kept clear but didn't, then she broke rule 11 with respect to Yellow and should be penalized.  But in any case, I don't think Yellow should be exonerated for breaking rule 11 with respect to Green, because it doesn't look to me as if there's any way Yellow could have kept clear of Green, even if Blue had responded -- there's just not enough space between Green and Blue and the shallows, for Yellow to go in there.  Thus, in my opinion, Yellow wasn't "compelled" to break rule 11 by Blue's breach of rule 11 and therefore she isn't exonerated under rule 43.1(a).  Bottom line: Penalize Yellow and exonerate Blue.

One observation, however.  If Blue could have responded, even a little, to Yellow's overlap to leeward of her, without risking running aground, she should have done so.  If there's a protest, and she can say, "Look, I responded to Yellow's overlap by heading up as much as I could, but because of the shallow water next to me, I couldn't go far enough to keep clear," that's a lot more persuasive than if she has to say "I didn't respond because, even if I had, I wouldn't have been able to keep clear."  Now she's arguing a hypothetical, and the protest committee might well say, Blue had to keep clear of Yellow and she did nothing to do so, even though she could have at least moved to windward 1/2 boatlength or so."  That discussion leads pretty easily to DSQ for Blue.

Hi Paddy,
There is a difference between calling for water and calling for room to tack.  Unless Yellow specifically called for room to tack, she does not break R20.  When Green chooses to pass Blue to leeward, she must also give Yellow room while Blue is an obstruction.  Green could choose to luff and pass to windward of Blue, but in doing so, she must give Yellow room to avoid running aground.  The shallow water is an obstruction and Yellow is within her rights to hail Green that she is in danger of running aground.

Rule 19.2 (b)  impacts you as you are overlapped therefore you must continue to provide room for green to maneuver to avoid the continuing obstruction.
Room does not include room to pass the vessel ahead, only room to remain clear of the obstruction.  Blue is not an obstruction.
You were not overlapped with blue until yellow overlapped both of you.  Yellow cannot call for room 19.2(c) however now and position#3 you have to keep clear of blue too.
A bit of a mess.  It would have been good for you to hail yellow prior to him overlapping blue "no room". 
You were a nice guy to let him in.   He / she owes you one.

I would look at the situation at Position 2 Yellow is entitled to space to pass on to same side as Green because Blue being an obstruction to both Y and G RRS 19 
So Green has met her obligation and at position three all the three boats are overlapped and RRS 19 no longer applies. 
The situation under review is over. Any further developments can be dealt with as per applicable rules and fair interpretation by the Jury based on facts.
Thank you Rob for taking us through the possibilities in the current situation.

Definitions

Obstruction An object that a boat could not pass without changing course 
substantially, if she were sailing directly towards it and one of her hull lengths 
from it. An object that can be safely passed on only one side and an object, 
area or line so designated by the sailing instructions are also obstructions. 
However, a boat racing is not an obstruction to other boats unless they are 
required to keep clear of her or, if rule 22 applies, avoid her. A vessel under 
way, including a boat racing, is never a continuing obstruction.

Therefore, blue is not an obstruction and yellow must keep clear.

Thanks for all the answers so far.  I should have drawn the shallow water line closer to the boats.  Blue would have been in about 0.2m under the keel an no room to move higher.

Hi Murray 
You’re absolutely right my bad. Generally where I sail “water” normally means room to tack. Didn’t think it through.
I thought it simple but Rob really defined it. 
It’s filed now for future use.

Rob, in dissecting your analysis, wouldn’t DSQ Yellow depend upon whether Yellow or Green becomes overlapped with Blue first?

I agree 100% that if Green overlaps Blue before Yellow, 19 turns off for  both Yellow and Green before it is necessary for room to be provided to Green.   In this instance, overlap doesn't transfer to Yellow because Green is not between Yellow and Blue.

However, couldn’t one argue that if Yellow is ahead of Green at 2 (as shown), but still both Green and Yellow clear astern of Blue, at 2 Green must provide Yellow room to pass Blue because Blue is an obstruction to both (both required to keep clear of Blue) and they are “at” Blue. 

In this case (Yellow ahead of Green), immediately after 2, Yellow and Green become overlapped with Blue simultaneously (as now Yellow is between Green and Blue) and as you say “POOF!”, obstruction-Blue disappears, leaving only the shoal continuing obstruction, 

Simultaneously with “POOF!”, when get “POW!” (for Batman TV series fans).  

Given the above, 
- Green ahead of Yellow at 2+, DSQ Yellow..
- Yellow ahead of Green at 2+, no boat penalized.

Ian, as you can see from the responses, your question is not as simple as you initially believed.

Simply stated, Yellow has got herself into a bad place.  She is windward and the keep clear vessel providing she has room (see definition "Room") to avoid the obstruction(s) 

No room to pass.  All she can do is follow blue however....

Blue is an obstruction (not a continuing obstruction).  Yellow must avoid her however she may only maneuver within her rights. Yellow is the giveaway vessel to both blue and green.

Yellow , windward, has no rights other than room (see "room" definition) to keep off of the rocks which green has provided.   Rule 19.2(b).

Green is not required to make any course change to permit yellow to pass blue however forced to change course to avoid collision with yellow (rule 14) may protest yellow under rule 11.  (also see definition "Keep Clear" which yellow failed to do as green had to alter course to avoid her)

Yellow may argue that:

1) she needed more depth.  (yellow is following blue which is in navigable waters) no need for more room.

2) had to avoid an obstruction (blue) (Blue is not a continuing obstruction therefore there is no obligation for green to alter course to provide room until there is evidence that she must do so to avoid collision with yellow.  Yellow should have slowed long before.

Green cannot protest under rule 20  as it is not applicable.

Yellow would loose the protest under rule 11 for failing to keep clear as green had to alter course to avoid contact.

Angelo is right -- both Yellow and Green are overlapped with Blue at position 3, so Blue is an obstruction to neither boat.  POOF, POOF!  For more on the general issue of the disappearing obstruction (without the continuing obstruction to windward), see Team Race Call F2.  That call has three different scenarios, and in all three, the boat that was entitled to room before the obstruction disappears is screwed after it disappears.  Team-race calls are not authoritative in normal fleet racing, but when the rules that apply in a TR Call are numbered rules from the RRS (as opposed to rules in Appendix D), the call-book writers are supposed to give an interpretation of the rules that would be valid for fleet racing as well as for team racing.  Call F1 is such a call, and gives the answer that a group of knowledgeable rules experts came up with, on this topic: POW.  

This is an interesting question. My answer is different to everyone else’s.

Firstly, from the diagram, it looks as if Yellow to windward may not be keeping clear of Green at positions 1 and 2. Is there contact between Yellow’s spinnaker or spinnaker pole and Green? Is it feasible for Green to continue sailing that course while astern of Blue? Can Yellow sail further to windward or is it too shallow?

If no rule is broken at positions 1 and 2, then I don’t agree about Yellow being DSQ for breaking Rule 11 at position 3. 

Although Blue is no longer an obstruction at position 3, the continuing obstruction still remains. Green is still required give Yellow room between her and the continuing obstruction, under Rule 19.2(b). The room is “The space a boat needs in the existing conditions … while manoeuvring promptly in a seamanlike way”.

Even though Blue is no longer an obstruction, it would still not be seamanlike for Yellow to collide into her. It also doesn’t appear to be seamanlike for Yellow to force herself between Blue and the continuing obstruction and to do so would likely break Rule 19.2(c). Blue’s presence, despite not being an obstruction, is one of the “existing conditions” that Green needs to take into account when determining how much room Yellow needs to pass the continuing obstruction.

The same would apply if there was a swimmer in the water. The swimmer may not come under the definition of an obstruction, but a boat cannot force another to run over them.

Teams Racing Call F2 is distinguishable because the boats’ courses there were not affected by another obstruction.

John makes some good points.  I was assuming that Yellow was keeping clear at positions 1 and 2 -- presumably her spinnaker clew is high enough so it doesn't actually interfere with Green.  If not, the whole question is moot: Penalize Yellow for failing to keep clear of Green at positions 1 and 2.  At position 3, Green is shown as having changed course to avoid Yellow, so I applied the definition "Keep Clear" to infer that Yellow is not keeping clear at that point.  

I like John's argument about Green having to give Yellow room at the continuing obstruction (the shallows).  He's right:  Room includes the space necessary to carry out the required maneuver, considering all the factors involved.  So if the overlap to leeward of Blue is inevitable, Green must give Yellow room to sail within that overlap, as John says.  However, John is apparently arguing that slowing down is unseamanlike, as Yellow could surely have released or overtrimmed her mainsheet, or put her rudder over hard to leeward and then back hard to windward to create drag, or done other things to slow herself, and avoided getting the overlap with Blue.  When one boat is required to give another boat room, the boat entitled to room does not get to decide how she wants to sail -- she must do whatever she can do, in a seamanlike manner, to obey the rules.  In this case, Yellow may well prefer to keep going fast and establish the overlap, but that's not her call.  Slowing and staying astern of Blue will accomplish the same result (keeping clear of Green), so slowing is what she must do if she can; and I assume she could have slowed, as Ian originally asked, "...  should [Yellow] have tried to slow down?"

Rob.
You are right on.
Yellow has no rights and must avoid blue and green and must do so by any means in a Seaman like manner.  Slowing your boat down is a Seaman like maneuver.
Green's obligation to yellow for room does not include room to pass.
Green is commendable for avoiding collision.
Because yellow forced her to turn is grounds for a protest under RRS 11

The argument, “Yellow could have slowed down”, raises some interesting points.

The main problem with it is that Rule 19.2(b) requires the outside boat to not only give room – they must give room between themselves and the obstruction. If Green requires Yellow to slow down behind Blue, while Green passes close outside Blue, then Green is not giving room between her and the continuing obstruction. She is only giving room behind her.

Expecting an inside boat to slow down would undermine Rule 19.2(b). An outside, right of way boat could refuse to follow the rule by arguing that the inside boat didn’t have to sail inside her.

There would also be a difficulty expecting Yellow to slow down in this scenario. Yellow’s spinnaker was already over Green’s deck. Easing sheets further to slow down will very likely lead to an entanglement of the rigging (she will need to let out the spinnaker as well as the mainsail). Putting her rudder over hard to leeward would inevitably cause a collision. Luffing will likely to cause Yellow to run aground. Yellow is sandwiched. I don’t know what type of boats these are, but if they are keelboats sailing with momentum, then the situation will be even more critical.

Rob, why doesn’t Q2/A2 of TR F2 support my position? Seems it’s saying exactly what I’ve been saying.

In OP drawing, pos 1-2 (applying wording from TR-F2), "... [Green] is sailing a course to pass to leeward of [Blue] ..." and I’d argue at position 2, Yellow is already past being “... at the point when B [Yellow] needs to commit to passing to leeward of X [Blue], Y [Green] is the outside boat and must give B [Yellow] room under rule 19.2(b). 

The obstruction does not disappear.
RRS 19.2(c)(2) while the boats remain overlapped, ... RRS 11 does not apply.

Wow, to think that this thread was titled "Novice Question"!  

In response to John's point, I agree that if Yellow cannot slow at positions 1 and 2 to avoid the leeward overlap on Blue at position 3, then Green must give Yellow room to sail to leeward of Blue as part of her room to sail between Green and the continuing obstruction.  It's an important part of the definition "Room" that it includes "space to comply with her obligations under the rules of Part 2 and rule 31 ...", and in this case Yellow needs room to obey rule 15 with respect to Blue.

 But I still think Yellow has to avoid the overlap with Blue if she can do so in a seamanlike manner.  I grant to John that when one boat is required to give another boat room to sail "between her and the obstruction", that does not require the other boat to slow or otherwise maneuver to avoid going between the boat and the obstruction.  But in this case, the right that John's argument depends on is for Yellow to sail between Green and the continuing obstruction, not for her to sail between Green and Blue.  So, although I like John's argument, I'm sticking to the idea that Yellow must avoid the overlap with Blue if possible to do so in a seamanlike manner, and if she can do so but does not, she should be penalized.

I think Angelo is right -- Yellow must bear off at position 2 to give Green room to pass between her and Blue, who is at that moment an obstruction to both of them, and she doesn't appear to be doing so.  So, there are two incidents -- one at position 2, where Green breaks rule 19.2, and one at position 3.  Assuming that Green has to bear off even more at position 3 to avoid Yellow, or, if not, that when Yellow goes between Green and Blue she gets so close to Green that Green cannot turn without immediate contact, then Yellow breaks rule 11 with respect to Green at position 3.  In the second incident, Yellow is not exonerated because ... there's no obstruction!

Wait!  What am I saying?  In the absence of the continuing obstruction, as long as Blue is an obstruction and Green is clearly sailing to pass to leeward of Blue, she must give Yellow room to also sail to leeward of Blue; but as soon as either Green or Yellow becomes overlapped to leeward of Blue, Blue is no longer an obstruction so Yellow is no longer is entitled to that room, and can be penalized for just being there!  So what good did it do Yellow to be entitled to room, earlier?  Not much, I guess.

BTW, some of the participants on this threat have pointed out that Green needs to obey rule 14, and of course, they're right.  This discussion, as is the case with many of these discussions, has concentrated on the rules of Part 2 other than rule 14.  

Philip.
19(2)(c) is not applicable as it states in part.... " Becomes overlapped between the other boat and the obstruction...."
1) as soon as the overlap occurred, blue was no longer an obstruction.
2) the overlap was not between the obstruction and the other boats.

Not applicable.

One last point.
The skipper of yellow is seeing that he is catching up to blue.  He has seen this coming long before point one. The skipper of  yellow has sailed himself into a spot knowing that he/ she has limited room to maneuver and should have seen it coming.
Yellow must avoid blue.
Yellow must also avoid green.
Yellow knew this all the way along.
Yellow bullied green into giving way.
Green was right to let yellow in to avoid collision.
Green has grounds for a protest.
 The skipper of yellow was either unable to foresee his / her predicament or didn't care.  He had to rely on a boat that had right of way to give way to avoid a collision.

Interesting novice situation! 

Since we put an continuing obstruction in the drawing it should mean something. If not it´s just blurring the situation. So, my interpretation of this scenario: Blue can´t sail closer to the shore without risk (remember, this is all security rules) so she has room under 19.2b in the third position. At pos one and two  Yellow is entitled to room to pass Blue from rule 19.2b as explained above. Then shifting to Green and Yellow giving Blue room to pass the obstruction when the overlap begins.

IF we imagine Green beeing advanced to Yellow Yellows right to room from the pos 1 and 2 would end at the moment that Green becomes overlapped with Blue. If Green sails a course that doesn´t allow Yellow to pass between her and Blue Yellow has no right to go in there...  Once Yellow becomes overlapped between Green and Blue she would have the right to be there, again from 19.2b. It´s hard to the see this work out in practice, but it might. 

This last one might more often occure in a starting situation when overlapped boats slowly approaches a boat holding a position on the line from behind. 

I think there are 3 points that we might be glossing-over here ....

#1: OK .. I "think" most agree that, at or before position 2, Green owes Yellow room to pass Blue.  Right? (assuming Yellow is ahead of Green)

Again, TR-F2 indicates ....

I'd argue that, at or just prior to 2, the room that Green owes Yellow is sufficient for Yellow to pass Blue on the same side as Green has chosen.  Therefore at or prior to 2, Green must turn down enough to open a space sufficient for Yellow to pass Blue.  19.2(b) provides Yellow room to pass Blue until Yellow becomes overlapped with Blue at which point 19.2(b) turns off, BUT Green is required to turn down and provide space at or just prior to position 2.

#2: At position #2, Green is a ROW boat relative to Yellow and Green has changed course ()

When Green changes course at position 2, along with 19.2(b)'s room to pass Blue, 16.1 requires Green to provide Yellow Room to keep clear of Green.  Yellow's Room includes space to comply with Yellow's other obligations under Part 2. 

Yellow's other Part 2 obligations include: 

At some point, Green's course-change puts Green on a trajectory heading away from Blue.  Therefore, any subsequent course-changes by Green back toward Yellow and Blue triggers 16.1 again, which gives Yellow room .. and Yellow's room includes space for Yellow to provide Blue room to pass the continuing obstruction.  

#3: 15 at position #2+

(I'll freely admit this argument may prove to be a stretch and more precarious, but I'll put it out for sake of discussion as I'm interested in other's rebuttals.)

At position 2+, both Green and Yellow simultaneously become ROW boat vs Blue, thus rule 15 applies between Green v Blue and Yellow v Blue at the moment and the "initial" moments after Yellow (and thus Green) becomes overlapped with Blue.   15 provides Blue room to keep clear of both boats.  To the extent that Blue can not move to windward to avoid Yellow, Blue's 15 room from Green includes her other obligations under Part 2, which includes her obligation to keep clear of Yellow.

Angelo, you are right.

RRS 15 does apply to this scenario.
How did yellow get there.

If green sailed windward to close the door on yellow then green is not providing room.

If green and blue are as shown and yellow is accelerating in from behind then yellow must plan to avoid the obstacles by going to leeward of green or slow down.

RRS 19.2(b) does not specifically provide room to "pass".  The rule states that they are given room to maneuver to avoid the obstacle(s).

16.1 is not applicable as green is maneuvering to decrease the risk of collision and providing more room for yellow.

Hi Mark,
I agree that 19.2(b) does not give room for Yellow to pass Blue.  Specifically, it gives Yellow room between Green and the obstruction (Blue). 
 In positions 1 and 2, Green and Yellow are overlapped and at the obstruction (Blue).  
According to R19.1 Rule 19 applies between Yellow and Green.
Here is where I disagree with Rob when he says "Green does not owe Yellow room under any rule". 

19.2(b) states that, when Yellow and Green are overlapped, Green (the outside boat) shall give Yellow (the inside boat) room between her and the obstruction, unless she has been
unable to do so from the time the overlap began.

Clearly, at position 1, Green was able to give Yellow room and therefore had been able to since the overlap began.  19.2(b) doesn't give room for Yellow to avoid Blue.  It gives Yellow room between Green and Blue.  
So, if Yellow has to slow down to avoid Blue because there is not room for her between Green and Blue, then Green breaks R19.2(b).

Mark, re: “16.1 is not applicable as green is maneuvering to decrease the risk of collision and providing more room for yellow”

16.1 does not say, When a right-of-way boat changes course [decreasing the risk of collision], she shall give the other boat room to keep clear.

16.1 simply says ...

When a right-of-way boat changes course, she shall give the other boat room to keep clear.

US33 says, “To change course means to change the direction in which the boat is heading or moving.”

Room in 16.1 is italicized, therefore 16.1’s room includes space for the keep clear boat (Yellow) to satisfy her other obligations under Part 2.  

IMO TRF2  seems to state otherwise ... that the room needs to be provided “ at the point when B [Yellow] needs to commit to passing to leeward of X [Blue], Y [Green] is the outside boat and must give B [Yellow] room under rule 19.2(b).”

How did yellow get there in the first place?
If green closed on yellow then green owes yellow room.  If yellow is there passing green then no 19.2(c) 

Q2/A2 of TR Call F2.  There is a difference between Green being bow out on Yellow (Case 117) and Yellow bow out on Green (Q2/A2 of TR Call F2 and Case  41).

Green owes the room to pass at the point Yellow has to commit to passing on the same side (that Green has chosen), which is before Yellow and Green are overlapped with Blue (while they are still both clear astern of Blue). 

PS:  This is also what Case  41 states: 

Which is different when the leeward boat is bow out as in Case  117

FWIW .. RYA has Case RYA2017-01.  

Question #4 is our case where they flip the wind from the opposite direction as shown in the drawing (and with more boats and with a mark, but the mark doesn't matter for our purposes).

Answer #4 indicates it is the same as Answer #2, which starts with the statement, "Because all the boats are overlapped and are at a continuing obstruction, they are all subject to rule 19.2(b)".

Why does WS Case 117 not apply?

Mark T., re: Case 117. 

IMO, Case 41 and Case 117, when taken together, illustrate the difference in how the rules play out depending on the relative positions of the the leeward-ROW boat vs the windward-KC boat as they approach the boat-obstruction. 

In 117, leeward is 3/4+ BL ahead of the windward boat and established her overlap with the boat-obstruction well before the windward boat.  That is not the OP situation of the thread. 

Case 41 and TR F2 describe the contrast to 117 where the windward boat is ahead.  Both 41 and F2 describe that the room to pass is owed while both boats are still clear astern of the boat-obstruction. 

Case 41 puts it ...

In consistent fashion and slightly diff way, TR-F2 puts it .. 

Ian.
With reference to the continuing obstruction, when did yellow become overlapped with green?
Before blue and green where against the obstruction or after? ( How far does the obstruction go?)