Years ago I owned an island in a lake in northern Canada. The lake was part of a river-lake system that stretched for a hundred miles.
There was an odd geographic anomaly way up the lake from me. There was an incredibly deep area toward the fjord-like end of this lake. I mean, it was several hundred feet deeper than anything else.
And this stretch never froze. I mean never, not even after long stretches of -50 F.
The open water meant that, in sub-zero conditions, there was always an ice fog over that area.
Long story short: there were several Indian villages along the lake, one up a drainage beyond this stretch. Indians kept an ice trail along the edge of the lake open for their sleds between villages. They ran traplines in the district.
Couple of guys were traveling the trail in the winter dark. They disappeared somewhere along there, never to be seen again.