Heron on alert on bank of River Frome

I ventured down to the river close to Ham Mill lock on the canal, which runs very close by through the Golden Valley. It has to as there is nowhere else in the narrow valley bottom.

I peered over a fence on the towpath and saw this heron waiting patiently beside the extremely fast flowing water. I think it must be hard for it to hunt in these conditions. 

A few minutes later a second heron flew upstream towards this point, but it appeared to veer away when it saw this heron. Seconds later this heron took flight over the water and directly upstream.