It looks like a whiteish patch under the eye, I'd say its a cormorant
Remember - the only stupid question is the one you don't ask.
See some of my photos at https://www.flickr.com/photos/181900595@N03/
Shags never embraced the inland waterway lifestyle like this cormorant.
Every day a little more irate about bird of prey persecution, and I have a cat - Got a problem with that?
As said it looks like a Cormorant it is fairly rare to see Shags on inland waters.
Pete
Birding is for everyone no matter how good or bad we are at it,enjoy it while you can