Such a shame that the majority of replies seem to suggest not taking any action (bar a radio message to QHM) .
Of particular disappointment is the attitude of the (professional?) skipper giving instruction.
I suppose it's a sign of the times nowadays...the solidarity once prevalent out on the water is fading fast.
As Douglas Adams said
" The Somebody Else's Problem field is much simpler and more effective, and what's more can be run for over a hundred years on a single torch battery. This is because it relies on people's natural disposition not to see anything they don't want to, weren't expecting, or can't explain."
There was obviously an SEP field in use around the sailboat ;-)
I would of had little issue trimming the outboard right up and edging in closer, especially with 1.2m under the keel and only 50m left to run.
Where I do my boating in Finistere, I often run into isolated coves to access secluded beaches. I often trim the engine up to just before the point that cooling may become an issue and slowly edge my boat(s) into shallow water. Sure, I've touched bottom on several occasions and, so long as your only going slowly, you can easily go astern and pull yourself free. No drama and no damage ever suffered since I normally have the someone on the bow which helps level out the trim meaning the keel touches and not the outboard skeg.
Incidentally, if QHM had been advised, the call to one of the local VOLUNTEER rescue stations would have probably been made... Possibly GAFIRS in Gosport.. These guys do not get paid for the work they do so in effect what could of been a quick lift off would (by the time the rescue boat got there and the tide dropped further ) have turned into a rescue operation whereby personel transfers could of potentially been required risking both rescuers and rescuees....
C'est pas l'homme qui prend la mer, c'est la mer qui prend l'homme....