A woman who was attacked by a dog during a pre-Christmas swim at a City of Cape Town coastal resort is in line for a payout from the council.

Fatima Carelse sued in the high court in Cape Town, which ruled on Wednesday that the city council had been negligent.

The owner of the dog, which was confiscated and put down after the attack, will have to share Carelse's damages bill with the city council.

Carelse went to Harmony Park, between Strand and Gordon's Bay, for a day out in December 2013, said Acting Judge Wesley Vos.

After putting up their gazebo, Carelse, her niece Zulfah and friend Emilio Nelson were playing with a ball in a tidal pool when a dog leapt in and "viciously attacked" the woman.

Sixteen-year-old Dylan Eksteen, who had brought the family pet to the pool, dived in to try to control the dog but it also bit him, said Vos.

After first-aid treatment, Carelse was taken to hospital.