Rarely moving and largely ignoring a small crowd, the seal had a future that was not looking promising, but the observations of a vet proved heartening.

Paul Partland of Cannon and Ball Veterinary Clinic monitored the animal throughout the day and said its injury did not appear to be life-threatening.

"I don't think the wound would be causing him any pain at the moment," he said.

"We're going to give him some space and reassess him; it's likely that he'll leave of his own accord during the night but we'll check up on him if he's still here in the morning."

While the animal's thick layer of blubber has been compromised, Mr Partland said there was a good chance it would survive.

"He's got a hole in his doona - he would be losing heat from his body so he's just resting and trying to warm up again before he heads back out," he said.

Usually found in Antarctic waters, the seal is likely to have travelled north in search of food.

If the seal had not returned to the ocean overnight, Mr Partland said it was important for people not to approach as it could become aggressive.