BALI - An Australian surfer has started a petition to free four dolphins which are kept in a swimming pool in a Bali attraction.

The pool is only 10m by 20m, and the dolphins are said to be almost blind from the chlorine in the water, reports say.

Wake Bali Dolphins, which is located on Keramas Beach, charges US$110 (S$149) for an adult and US$100 fora child to swim with the dolphins.

It also charges a US$89 "watching fee" .

"You are invited to not just watching but rather interacts directly with dolphin through hugging, kissing, and really swimming with dolphins," the attraction writes on its website.

Sydney surfer Craig Brokensha said he discovered the facility while on holiday in Bali.

On his petition, he wrote: "After initial protests when Wake Bali opened last July, the resort still remains open and the dolphins remain trapped in a tiny chlorinated pool.

"This is a request for Wake Bali Dolphins to free the dolphins and allow them to be re-introduced into the wild, where they belong."

The petition had garnered close to 28,000 supporters by Monday.

Others had complained about the attraction as far back as a year ago.

The Bali Animal Welfare Association said on Facebook in July 2014 that it received a call from a distressed tourist who told them that there were dolphins being held in a pool in Keramas.

It said: "More than 50 per cent of dolphins who survive the trauma of capture die within months. Half of all dolphins die within their first two years of captivity."

It urged tourists to boycott such dolphin pools.