A seal found with 30 shotgun pellets in her head has lost the sight in one eye and is still quite poorly.
The adult female was taken to East Winch Wildlife Centre near King's Lynn in Norfolk after she was found off Gravesend in Kent.
RSPCA inspector Rob Melloy said she would be permanently blind in one eye and it was "touch and go" whether her sight would return to the other eye.
He said on Saturday she was eating fish, which "was a good sign".
The shotgun pellets showed up in an X-ray of the seal, which is suffering from various infections.
Mr Melloy, who is the RSPCA inspector for Norfolk, said such an attack on a seal was fairly rare, and it was only the second time in five years that he had come across it.
He said the Conservation of Seals Act prohibited the shooting of seals unless a specific weapon, such as a very high powered rifle, was used.
"Certainly using a shotgun, as has proved with this seal, is nothing but cruel because it hasn't killed the seal, all it has done is caused it immense suffering," he said.
He said the injured seal was on painkillers and antibiotics for her wounds, but there were fears that some of the pellets could move further into her body and cause further injury.
He said it was unclear at this stage whether the seal would survive.