First thanks for getting back.
I had installed the game in C/Program/Ubisoft, C/Program (86)/Ubisoft and even C/Ubisoft and it was always the same crash at always the same
P key stroke and 21 ft depth. Hmmm Didn't make sense-but I had a hunch it was a hardware problem. What my new computer doesn't have but my old legacy XP machine has is an after market sound card.
So I unchecked in Sound Options the 'Realistic Sound Travel Time' box. (I had always enabled that in many re-installations.)
No more crashes.
Fingers crossed and touch wood.