The cat that entered a dog swimming race in Sydney's northern beaches on Christmas Eve walked away with a gold in his category, and he celebrated with a Christmas swim.

Glenn Druery has declared that his 11-month Tonkinese, Gus, came first in the cat category in the Scotland Island Dog Race, as the only feline to enter.

Gus came first in the cat category in the 2019 Scotland Island Dog Race.

Gus also beat quite a few of the dogs in the annual 550-metre swim between Scotland Island and Church Point Wharf on Tuesday, Mr Druery said.

"We started a little up-wind from the rest of the dogs, which gave us a bit of a lead," Mr Druery said.