Nothing wrong with getting out and wetting a line, its a bonus to catch some fish
You could have seen a mudpuppy, salamander or even an American Eel (http://www.gen.umn.edu/research/fish/fishes/american_eel.html). So I don't think your crazy and it is possible. These eels can even crawl on land. I saw one a few years back on the St. Croix river in Wisconsin. So I would'nt be so surprised if you saw one. Just think most people never see one in their lifetimes, so thats a plus
Who knows what crazy critters are swiming around Minnesota waters with all the foreign stuff around now, so I wouldn't rule that out :)
D.A. that lamprey would sound a little more like it. I haven't seen one myself, but it seems more like what he was describing.
I had an interesting run-in with local wildlife myself this weekend down near Chatfield. I was fishing a very small stream and was walking through a shallow riff when I almost stepped on the biggest snapping turtle I have ever seen, must have weighed 50-60 lbs. He was just sitting in a shallow part of the stream next to a deeper pool. When he found out I wasn't going to hurt him, he slowly made his way into the pool and swam under the bank. Probably been living in that river his whole life.