Butt's Tubes offers flatwater tubing. You get a big inner tube, you plop down in it, and you float along for about an hour. Along the way are some itty bitty rapids that you so want to go over to make it more exciting, but you need to be careful or you'll end up hitting your butt on a rock, which can be slightly painful. Most of the way is very slow, which can be either really relaxing, or just plain boring. The water is pretty shallow so sometimes you're able to walk along the bottom. You can also stop yourself at rocks along the way to sit out or picnic.
Towards the end are some big and fun rapids, that with some careful craftiness, you can go on multiple times - just stop yourself, climb up on a rock, and then go down the rapid again.
If you're wearing flip flops, make sure they're tied to your feet or they'll float away. Or be super prepared and bring those water shoe things.