Payette Lake at McCall is glacier-cut, cold and over three hundred feet deep, and people have been reporting something long moving in it since the 1920s, when loggers said they saw a log that swam. The name came from a 1954 contest run by a local paper to give the creature something better than what it had been called. Idaho has kept it good-humoured ever since; there is a winter carnival and the name is on half the town. The lake is spectacular whether or not anything is down there.
Payette Lake, McCall (Valley County, Idaho)
See it on the map