Looking for some advice here.

I've decided to get an inflatable PFD for wading. I'm wondering if I should go with the auto or the manual unit? I'm leaning to the manual because I figure that it's possible for the autos to go off because I've waded a bit deep or its raining hard. I also wouldn't want the thing to go off just because I've taken a bit of a dunking in an otherwise safe situation. Given my complete lack of experience, I don't know if those concerns are valid.

Also: Has anyone had experience with the basic Cabelas units?