Mud Island is a tourist trap of inordinate description. The museum part is nice enough -- a history of the Mississippi River with fairly helpful presentations. At the end, you can wade in a scale model of the river, from Minnesota to the Gulf of Mexico, all the while avoiding pickpockets and ice cream vendors. Don't try to swim in the Gulf. We did when I was a kid and the cops threw us out. I had to be all wet while watching Superman III. Don't ask.
I will ALWAYS list the River Ducks under tourist traps......
I wouldn't mind having one of their trucks though...
Unique Suggestions: www.memphisducks.com
They used to travel up and down the Mighty Mississippi. Now they just take tourists for a round trip of a few miles. Somehow, I don't think the feel onboard would be anything like it used to be.