Confidence: I'm as sure as I can be.
Notes: A pair of Mute Swans that swam over to where I was stood, maybe in the expectation of being fed. When they realised I was not a source of food one of the pair started to dredge water weeds and decaying leaves from the lake bed, deposit them on the bank and sort through the mess. I presume it was looking for food.
This is the first time I've seen the ridges on the lower half of the beak.