Maybe the shallow water wasn't an obstruction but the bottom under it was, as demonstrated by the other boats aground.

Rule 19 deals with giving room at an obstuction

19 ROOM TO PASS AN OBSTRUCTION
19.1 When Rule 19 Applies
Rule 19 applies between two boats at an obstruction except
(a) when the obstruction is a mark the boats are required to
leave on the same side, or
(b) when rule 18 applies between the boats and the
obstruction is another boat overlapped with each of them.
However, at a continuing obstruction, rule 19 always applies
and rule 18 does not.
19.2 Giving Room at an Obstruction
(a) A right-of-way boat may choose to pass an obstruction on
either side.
(b) When boats are overlapped, the outside boat shall give the
inside boat room between her and the obstruction, unless
she has been unable to do so from the time the overlap
began.
(c) While boats are passing a continuing obstruction, if a boat
that was clear astern and required to keep clear becomes
overlapped between the other boat and the obstruction
and, at the moment the overlap begins, there is not room
for her to pass between them,
(1) she is not entitled to room under rule 19.2(b), and
(2) while the boats remain overlapped, she shall keep
clear and rules 10 and 11 do not apply.

This RYA Appeal gives guidance if you are in doubt.

RYA 2011/1
An inside boat that reasonably believes that she is at an obstruction and acts accordingly is entitled to room from an  outside boat. The inside boat is not required to endanger herself in order to claim her entitlement to room. If the outside  boat disputes the inside boat's entitlement to room, she must nevertheless give room, and then, if she wishes, protest.

I think John is mostly right. However, I think you also had the right to maintain your proper course and while you couldn't luff a boat into an obstruction, you *can* hold your course. Consider that in rule 20, the only hails for an obstruction are "room to tack" and response of either tacking immediately or responding "you tack." This clearly doesn't apply off the wind because frankly a boat has the ability to head up and pass behind a boat that has ROW. If it is true that at the time you were in 24' of water, the other boat had the obligation to keep clear - either by taking your stern or heading up. If they thought they were on the verge of running out of water, it's up to them to decide how to handle that.

I don't agree. Giving room at an obstruction may involve the ROW boat changing course. She has to give enough room to the overlapped inside boat to clear the obstruction and if maintaining course does not do that, then she must change course, maybe even gybe.

The OP could protest, but would only have a chance of winning if they knew that there other boat knew that they could pass closer to there obstruction. Hard to prove... GPS track of them passing closer to there obstruction in danger tide and sea state ?

Greg Wilkins

Email: gregw@wiltel.org

Said Created: Today 04:57

Agree

The rules generally deal with physical facts, time, distance, depth, and what boats actually do, not with mental states or what people on boats thought or knew, much less what one boat 'knew another boat knew'.

If the outside boat protests, its going to be a straight up fail to keep clear protest, and she will need to persuade the protest committee that there was sufficient space for the inside boat to pass between herself and the obstruction.

The answer may depend on whether the collision regulations applied as the part of RRS is off.

In the UK we have RYA case 1968/11.

"When the nature of a continuing obstruction changes because of a projection or shallows, these features form part of the continuing obstruction, and a boat that has properly established an inside overlap is then entitled to any necessary additional room"

"SUMMARY OF THE FACTS
"W established an overlap on L between positions 1 and 2 when L was one and a half to two boat lengths from the shore.
Several boat-lengths ahead, some shallows extended from the shore from a brickwork structure. W hailed ‘Water’ but L, although acknowledging the hail, made no attempt to give room and W ran aground.
W protested L under rules 19.2(b) and 19.2(c), but the protest committee dismissed the case, stating that W had tried to force a passage between L and the shore, L having been clear ahead when she came within three hull lengths of the obstruction. W appealed.
"DECISION
"W’s appeal is upheld. She is reinstated, and L is disqualified under rule 19.2(b).
There is no zone at an obstruction - continuing or otherwise - at which rule 19 applies, and so the situation when one of the boats comes within three hull lengths of an obstruction is not relevant. Rule 19.2(c) says that the inside boat’s right to establish an overlap between a boat and a continuing obstruction depends on whether there was room, as defined, to pass between the boat that was ahead and the continuing obstruction at the moment the overlap was established.
When W established her overlap, there was room to pass between L and the shore, and the overlap was therefore properly established. L initially then gave room as required by rule 19.2(b) but ceased to do so when the projecting shallows were reached. These shallows and the adjacent brick structure were part of the continuing obstruction, and W continued to be entitled to room."

I think this makes it very clear that the ROW boat must change course if necessary to give room to pass an obstruction.

Here is an old thread that touches on this issue.

https://www.racingrulesofsailing.org/posts/125-redress-possibility-after-being-run-hard-aground-w-o-damage

I actually wrote a submission years ago adding being “run aground” to “Injury and physical damage” in 62.1(b) .. but that was rejected (at that time .. might be worth a resubmission?). 

I think the concepts around what I’d call “Invisible obstructions” are interesting.  I think there is a dedicated thread someplace about them ..,but can’t put my finger on it.  If anyone finds it .. please post the link. 

Also, in shallows in mixed fleets … you can have boats of significantly diff drafts.  If the shallow is 6 feet, one boat draws 7’ and the other 4’, are they both at an obstruction? 

> If the shallow is 6 feet, one boat draws 7’ and the other 4’, are they both at an obstruction? 
One might also consider boats of very different length: an object 3 feet wide is clearly an obstruction for an 11 foot boat, but perhaps not for a 110ft boat. 
I'm not sure I can construct a scenario where this makes much difference though. RRS 20 doesn't require the hailed boat to be approaching the obstruction, and one might interpret RRS 19 to be applicable if either boat is at an obstruction. It certainly doesn't say both. Also if the object is sufficiently small not to be classed as an obstruction, it doesn't seem a problem for the inside boat to have to pass the opposite side to the ROW boat.

If I may digress though, this does remind me of a favourite tale. My informant is in a high performance 12 footer which has a notably long high aspect ratio daggerboard. The scenario, decades ago, is an evening race, tacking up the banks of the Hamble.  Our heroes are following a friend in a Quarter Tonner. 
"Getting a bit close Simon" 
"No problem, he's got an echo sounder" 
[FX:crunch]
on comparing notes afterwards it transpired that the twelve foot dinghy drew nearly a foot more water than the Quarter Tonner.

I appreciate all of the comments. I'm not sure I have a clear picture of who had the ROW. When an obstruction is on the surface, it's easy to gauge distance and clearance, even if it's a continuous obstruction like a seawall or an anchored barge. The boats that were aground were a good distance away -- 100M or more. In a narrow channel where two successive channel markers clearly provide a visual boundary of channel vs. shoal by drawing an imaginary line between them, just like we do at any start of a race between the RC and the pin. But when the shoal is generally "over there" somewhere, and we're half a mile from the shoreline, at what point does the inside boat take over ROW, vs. using "shallow-ER" water to windward as a crutch to force us to sail below our proper course? As I mentioned, we had 24' of water beneath us at the time we hailed Leeward. It was a 30NM race, and we both draw about 6-7'. Yes, there was a shoal "over there" to windward, just like virtually every inland race has shallowER water and eventually shoaling closer to the shoreline. This just feels like a very grey, undefined area to me. 

Right of way doesn't change. As leeward boat you always had right of way. BUT... right of way isn't unlimited, and the rules of part two and part three limit what right of way can do and place obligations on the right of way boat to give room in various situations. 
In particular RRS19 and 20 give an obligation that the ROW boat must give the other boat room to avoid obstructions, and this is not negotiable. ROW must give room, even if she thinks it's not justified. You can't argue on the water whether or not room is justified, you can only give the room then protest. 

Steven, with that extra information, it does sound like the other boat may have been stretching it to say they were at an obstruction.

However, I think a key thing for you to ponder is would it have made a difference?  Where ever the obstruction was, you were never going to be able to use it to stop the other boat sailing over you once she had the overlap. If you had pushed the other boat up, eventually RR19 would come into play and you'd have to give room.

If it had been open water do you think you could have defended? Would you have been prepared to luff the other boat to a stand still?  Or could she have sailed up and over you anyway?  It sounds like she was already overlapped from a long way out, so you were going to have trouble defending regardless I think.

If you think you could have defended because there was no room between you and three shallows, then RRS19 begs to differ. It says you must give room.

Does your club have mediation provisions? If so, then maybe you could have protested and asked for mediation on the day. That way the other boat would have had to at least explain in front of you and a mediator why they could not have come up at least a bit. You could then accept the mediators decision or go to a full protest depending on what you heard.

Edit: oops posted twice. Deleted slightly longer version

Normally we expect an obstruction to be a visible object, so there should be no need for a boat needing room to pass one to make a hail - the ROW boat can see the obstruction and can see how much room she needs to give.

Shoal water is a different situation as competitors can't see how shallow it gets and where. You don't know for sure when you're "at" the obstruction. Seems like a hail, although not required, would be appropriate. And I think for safety reasons benefit of the doubt should generally be given to the inside boat, especially if she has the deeper draft.

The subject of obstruction 'somewhere down there' has not been addressed by the WS.
Rule 19 applies "at an obstruction except...". RRS 19.1(a) does not apply here.
In this example, we could safely say that the boats were not at the obstruction and in deep water for the boats to sail in.
Kim

Kim, we don’t know how steep the slope of the shoal is, or if the shoal has grown since it was charted.  The windward boat might have a deeper draft .. or maybe a torpedo bulb at the bottom that would cause more damage to the boat if she is grounded.  What is the nature of the bottom?  Mud?  Sand? Rocks?  

The windward boat might have local knowledge (paid for with paint from the bottom of her keel) that the leeward boat didn’t. 

I think the nature of a shoal’s invisibility, increases the “space a boat needs in the existing conditions … to maneuver in a seamanlike way”. 

Angelo, in my original post, the bottom was mud, so damage wasn't likely. 3 other boats ran aground on that same race, a few hundred yards to windward of where my encounter occurred. One boat was stuck for more than an hour and had to be towed off. The Chesapeake Bay and its tributaries are mostly mud on bottom. I have never heard of a boat experiencing damage from running aground on the Chesapeake, in modern times. 

Steven, FWIW, I didn’t  see “mud” or “a few hundred yards” in your OP. 

I too race in the Chesapeake ..  and have seen lead keels damaged after running aground here.  Tips get broken off of bulbs while boats turn to extract themselves.  Lead is soft and is damaged easily. 

If you were OD racing .. and you had boats of your same specs aground “a few hundred yards to windward” … then yea … maybe W was being too cautious. You could have protested them and used that as evidence that they were not yet at the obstruction. 

However if you are in mixed-fleet racing .. boats can have vastly diff underwater depths and appendages. I see 2 Cal 25’s aground … that tells me it’s 4’ there … but I draw 6-1/2 in my J105 … which could be 100yds further out. 

Bottom line in my mind is that you did the right thing giving W room. If you thought it was excessive, then you could protest them … but never refuse to give a boat room at a shoal that they request. 

>  you did the right thing giving W room. If you thought it was excessive, then you could protest them …
Practically speaking surely there is no choice. If windward state that they are not going to luff then all leeward can do is accept it and protest. They certainly can't go barging into them. Those days are (thankfully) long gone.

Once, when racing in a mixed fleet on unfamiliar waters, a boat slightly ahead and to windward suddenly ran aground and came to a hard stop. As we passed them we hailed "how much do you draw?", to which came the not so helpful response "too much!"

Don't forget Rule 1:
1. SAFETY

A boat, competitor or support person shall give all possible help to any person or vessel in danger. 

A call for water or room at an obstruction is a notification that the hailing boat is or will very shortly be in danger. 
Give room (or hail you tack if appropriate) and protest if you believe the hailing boat broke a rule or was not entitled to use the hail.
All possible help would include moving to allow a course change by the hailing boat so it can avoid the danger.

Steven .. also around the thought  “no damage when you touch bottom in the Chesapeake” because it’s mud and sand ..

In a Wed Night race this year I was in a downwind overlap duel with another 105 as we approached a turning mark. Neither of us remembered how low the tide was when we jumped on our boats.  We both hit bottom with speed and were able to turn and sail off pretty quickly after a couple more bumps. 

I dive my boat myself … and so I can see that episode removed all the bottom paint and some of my barrier coat from the front-bottom of my bulb. 

To repair that, we are talking a haul out and hang on the lift for 1-2 days.. as putting the barrier coat .. letting that dry and then bottom paint as well takes that long and you can’t block it as you need to work under the keel bulb. 

That’s not cheap.