I was never able to make out a head or a tail so I have no guesses either-
I�ll be curious what someone who may know that river what it could have been-

And btw guys, the two videos are the same -

Fake. No head. No tail. No dorsal fin.

By the way, the Missouri River is in the title, the description, and also mentioned in the audio.

IT'S THE MISSOURI RIVER, in case you didn't notice.

Further reading mentioned the pallid surgeon, a rare endangered species that averages 30 to 60 inches and 85 pounds. It occurs in the Missouri and Mississippi rivers in the state. The picture showed no dorsal fin. Seems to me this might be the fish in the video. It did not mention the length.

Read the comments below the video.

It's a channel marker and it's not moving. The current gives it the illusion that it is, but it's not. Their boat keeps drifting away from it and they have to drive back to it, but it's all just an illusion.