Flathead Lake 1993 — my uncle saw it twice and stopped fishing there

Okay so my uncle fished Flathead Lake his whole life, grew up on the Polson side. 1993, late August, he's out before dawn and something comes up maybe 40 feet off the stern. Not a wave. Not a log. He said it had a neck. He didn't stick around to count vertebrae. He went back two weeks later because……