I wish I had a nickle for every time I've heard this story. The first time I heard it was when I was a kid back in the 70's during the CB craze. I talked with more than one diver who did repair work on locks in the Ohio River around Louisville who told me the same. I have heard the same stories countless time over the years. No doubt these guys have come across some monster kitties, but I think the size gets embellished in the excitement.
I can't blame them though. If I were diving on a dam and brushed against a 60 Blue kitty I'd soil my drawers as well. And it's size would have grown to 300 pounds by the time I got out of the water.
I've heard the same story about the dam at lake Burton.