I used to run into one on Sneaky Snake quite often. After you drop down into Sneaky, make the left, and then go over the first little hill, he used to sit at the bottom of the backside of that hill. He was there so regularly that I'd look for him while on Snake Ridge approaching the entrance to Sneaky. He was about 5-6 feet and would always slide into the water before I came too close.
I've never seen Big Mamma out of the water and hope that I never do.