I've decided the injured cygnet looks like someone riding a scooter when he paddles about, because he makes big thrusts with just his right leg. So, *he's* Scooter. Also, he's still swimming about. Haven't seen the family for about a week, but they were near the Wooden Boat School again yesterday afternoon and this morning. Scooter is in the middle preening. he's obviously smaller and less developed than his siblings.
Scooter was waggling his injured leg a lot. I wondered if he was working out how to make it do something useful. It appears that the lower joint doesn't work, but he was able to slap the water with it. Anyway, he did manage to lift himself out of the water like his parents and siblings, and flap his rather small wings. I haven't seen him do that before.