A white swan has been turned black by what is thought to be printer toner dumped in a pond.
The mute swan was rescued from the water in Westbury, Wiltshire, covered in a "black powdery substance".
It was taken to RSPCA West Hatch where staff said it will take "quite a lot of Fairy Liquid to get it clean".
RSPCA Inspector Steph Daly said: "I was horrified because it looked like a black swan. We're still really baffled as to what this substance is."
The "distressed" bird was spotted preening and trying to clean the substance off in a pond off Mane Way on Friday before being rescued on Saturday.
Insp Daly said: "We were really concerned because of the state of it.
"We assumed it was oil but it's more powdery like photocopier ink toner."
The charity said staff were "busy with the job of washing the substance off" but with each wash taking 30 minutes, it was "labour intensive".
"He's been washed a number of times but it's not all off yet," Insp Daly added.
"Out of all the washing up liquids, it's only Fairy they use and they've put a shout out for donations because they get through quite a lot."
The charity is also concerned for the swan's mate which "managed to fly away" and is appealing for anyone who sees "any birds in a black substance" to contact them.
The Environment Agency said the "pollution was contained and not likely to worsen".
"It sounds like there was a deliberate act of someone disposing of something they shouldn't have done," said Ian Withers, from the agency.
"We will follow up and try and find the perpetrators."
Persimmon Homes Wessex, which owns the land, said it will "work closely with the local council to help find a resolution".