It is hard to tell from the photo without seeing the full context of how the wings are being used. Swans exhibit this behavior if they are: bathing and trying to get the wings and body wet, juveniles learning how to fly or swans that are being chased and beaten by another swan and trying to get away, but stressed or tired from trying to escape. If they all left together and are swimming normally, it was probably bathing or trying to fly behavior. If you see any further signs such as being chased and not allowed back in the water or too tired to eat and swim, then the bird needs someone to capture it and have it examined by an experienced bird/waterfowl veterinarian. The Regal Swan