Marsh St. John's Wort

I had a little trouble getting this identified, but am pretty sure I am correct. I don't think it's terribly common.
We had a nice visit to the edge of the reservoir. We were completely sidetracked by the abundance of wild blueberries and ended up picking quite a few. Most of the blueberry pictures did not come out. I only have this picture of a single berry in extra photos.
The other extra photo is the reservoir as viewed through the trees and blueberry bushes.