Well, I guess I'm getting a smack down for whining about the crowds. Now we've really got something to pay attention to.
When I checked the dip stick on the tranny this morning, seawater poured out. Not good. I may have said something else under my breath so as not to alarm Christine. The tranny oil cooler must have failed and allowed cooling seawater to enter the tranny and displace the oil.

First, let's tally up our lucky stars:
It didn't fail at some critical current or rock strewn point like the East River or the Watch Hill Passage.
It appears to have run for some number of minutes or hours on seawater alone, one tough tranny!
We are safely at anchor with three other boats we know to help or provide morale support.
It is a weekday and we have internet and phone signal so within minutes we had a picture of the part to the tranny repair shop in Topsfield MA and shortly thereafter a replacement cooler being overnighted to Block Island from Hansen Marine in Marblehead.
I was able to bypass the cooler with hoses and fittings on board so we can at least run the engine to top up batteries and make hot water while we wait for a replacement.
And, drum roll please, after draining the water and putting in fresh oil, the tranny is still turning. Of course I'll need to flush it multiple times because the fluid looks like a raspberry milkshake instead of cough syrup. And to be on the safe side, we may be looking at a rebuild in the fall.
But, given the above, this could have been waaaaay worse.