I can't believe you know about that guy. I hear it's a sturgeon. I actually based my deviation Ain't No Such A Thing [link] on a conversation between my Brother and I who had claimed to see it but was unable to tell what it was at the time. We joked about it being a giant turtle and the reason no one could find it was because it would float around looking like an island.
I read the Sturgeon theory somewhere and about someone finally getting pics of the thing as well or perhaps they caught one. I'm not sure. It was some time ago.. I do know that they are a bottom feeder. I also got read the riot act when I got caught using corn for bait when fishing up there because the things are protected to the point that you are not allowed to use corn, dough balls or anything like that.