A couple of those serene swans put a dent in their reputation. ( photo / image / picture from Kildale's Garden )
Swans can be very aggressive especially during mating season. I certainly wouldn't like to get between those two as the wings do quite a bit of damage. I've seen a cob take another by the neck, pull its head underwater and then beat it to within a inch of its life. There have been stories of swans drowning little dogs who have been swimming in their territory.
Yes we have a couple of swans that nest near a park in our area. You don't want to get to close as they will come after you. They are beautiful birds.