Human divers, brr!
Actually Lake O. isn’t too bad, rarely ices over. I think the first to swim across was Marilyn Bell (and afaik she’s still alive).
I’ve never felt the rapture of the deep, the cold is just an extra incentive not to try it. :^) The Great Lakes (probably other than Superior) tend to be pretty good, once they warm up, and I’ve been quite comfortable swimming in September. October can be wade-able. This year the water never really warmed up, which has meant almost no snow at all. I’m for it. :^)