We did a dive in Cochictuate about ten years ago and it was nasty. We were doing a rescue class and we were feeling lazy and decided to try and do it locally. It was mid summer and at the surface the water was about 80 degrees, about twenty feet from the shore we were in at least 40ft (the flag line was just dangling in the blacknes )of black cold (A few numbing thermoclines) water. It really slopes off in a hurry. I'm not sure we were allowed to be diving there in the first place and I have never found a reason to go back. I do know that some of the FD Dive teams Ice dive there.
Paul