Without seeing the actual injury, it does sound like a similar injury that we have seen from swans bitten by turtles. The swan needs to be looked at a by a veterinarian as the webbing needs to be debrided (removed if hanging) and an antibiotic administered. A swan's foot has a lot of capillaries in the webbing and any infection in this area could turn systemic which could cause the swan to become seriously ill or even die from sepsis. The Regal Swan