Fresh water doesn’t have marine organisms that destroy wood. ...........
That’s why! I wasn’t sure what it was. I remember reading somewhere that being water logged for so long all the cellulose is broken down and dissolved away. Apparently this makes it a very tone rich wood to make musical instruments out of. Cellulose deadens the tone and vibrations.
When they discovered this quality from these great lakes timbers is when they think they actually found the secret to the Stradivarius. They think Stradivarius soaked his wood for several years before dry curing it. This has of course been a mystery for a long time.