Sunset Ahead of the Storm

We have a flash flood alert for tonight's storms which made for an interesting sky up in Benedict.
This is my first landscape shot with the new lens. I experimented with a very low iso so that I could do a sort of timed exposure to soften the water. The lowest that I was able to set the aperture was higher than I expected, I wonder if there is a setting off or if that is the limit for the lens.
The extra is my grandson who kindly sat for a quick portrait with the new lens. He was doing a magic trick at the time.