This is a juvenile Great Crested Grebe, and it looks like he has bitten off more than he can swallow.
In fact it was the adult Grebe that caught this large Tench, and then gave it to one of three youngsters he had following him.
I thought the fish was too big for him to swallow and I think at times the grebe also thought that too. However after about ten minutes of struggling and throwing the fish around it finally, very slowly disappeared down his throat.
This was cropped down very hard from the original image so not sure how much detail it will have left.
