We saw 1 poor guy with that problem on a naturist beach in the South of France, he stayed in the water to endeavour to put things to right, whilst his wife did what she usually does ... turned over and went to sleep !

Talking about this makes me think of the film Kevin & Perry when he gets a stiffy on the beach, crawls into the water and he leaves a trench ha ha  😉

With all due respects to the erectionists  - and before this post becomes hijacked let me kindly point out that I headed it in the plural - am I the only man who worried about the opposite happening as well.  Opposite of erection - deflation? That was the point I was making - erected, deflated - it doesn't matter.  Oh, bliss!

I have never been worried about penile deflation on a beach.  That does not mean it does not happen especially when lying down when the penis can seem to retract into the pelvic cavity only to hang down again when you stand up.  Don't forget that the penis is also used for passing urine and tends to be fuller when your bladder is full even to the extent of being erect when your bladder is very full (early morning syndrome); if you have recently passed urine and have an empty bladder the chances are that your penis will be less full and be smaller than it sometimes is.  Deflation is only a problem when you want to get an erection and can't; then a little patience is required.  I can't speak about real impotency as it has not affected me yet.

Now you always wanted to know that didn't you?

Gordon.

ISTR that one of the prostate gland's functions is to block the urethra during sexual intercourse to make sure that the discharge of seminal fluid from the uterus masculinus goes out through the penis and not back up into the bladder.
It is quite possible that during times of high bladder stress the prostate my come to the assistance of the other valves in the system to prevent unwanted urination.
In this case a likely side effect would be a partial erection (or more).

Now you always wanted to know that didn't you?

I did - Gordon - thank you!

I have never had an erection on a naturist beach but have seen one or two. Mostly the men headed for the water whilst covering it with one hand.
As to having an erection whilst asleep, I was returning from Tokyo many years ago on a BA flight that had to stop at Anchorage as they had no polar survival kit on board which apparently was mandatory.
We had to wait eight hours for a JAL flight to bring one from London.
In the meantime all we could do was sleep on the floor of  the airport lounge, first class went to a hotel of course.
I must have slept for 2/3 hours and when I woke up some of the men I was with asked me if I had had enjoyed my dream. Only after they had kept this up for half an hour did one tell me that I had been lying on my back snoring with a raging erection under the thin blanket, which was obviously the high point...
I was initially very embarrassed but then thought what the heck, everybody gets them so what's the big deal. Not quite the same as lying on a beach naked however but because of the situation it was probably all the more obvious.