Yup, it's a swan.
In the UK, it's a curious fact that to eat a swan you have you apply for the Queen's permission first - because she 'owns' them all.
And as Crossbolt says, dogs and swans do not mix very well. I've seen dog owners moaning about the 'vicious' swans down at the park (the swans generally have eggs or young close by).
Personally, I find it quite amusing watching an adult swan going mental at folk walking their 4 legged turd machines.