What's this in the river?

We had a run out this morning to Hexham, and a walk along the river bank, and back through the town.
Hexham is a lovely old market town, and a place to walk along the River Tyne.
The river banks were full of people playing,picnicing, dog walking,
and having BBQs.
We spotted lots of Minnows in the water, who didn't seem at all frightened of this large snake which was watching them.