Protestors stripped down to their trunks and swimming costumes to push for Clontarf Baths to be opened to the public.
Around 40 north Dublin residents assembled outside the baths last night.
The owners of the 132-year-old seawater pool recently refurbished it at a cost of €2.4m.
However, it has been more than 20 years since the baths have been open for public use.
The Green Party's Donna Cooney, who organised the protest, told the Herald the baths' operators needed to fulfil their planning obligations by opening the pool to the public.
"The campaign to re-open the Clontarf Baths has been a long, hard-fought one," she said.
"For years, the baths lay derelict and became a dangerous eyesore.
"The refurbishment of the baths seemed to be the answer to locals' prayers, and an end to the saga was in sight.
"Unfortunately, it has just presented a new set of problems."
Ms Cooney said the adjacent restaurant and cafe bar were needed to make the baths economically viable.
"It is not good enough that the restaurant and cafe have opened while the main swimming facilities remain closed off," she said.
Other locals expressed the importance of the baths to them.
"People around here have a great emotional attachment to the baths," said Hilary McCaughey.
"Many children have learned to swim here and it means so much to the community to have them re-opened for public use.
"It's just a crying shame that we can't use them."
Meanwhile, broadcaster and businessman Bobby Kerr has plunged into the cold water, becoming the first person to swim in the baths since their redevelopment.
Mr Kerr told the Herald he went to the pool to interview owner David Cullen for his Newstalk show Down to Business, but while he was there he decided to take a dip.
"I decided I wanted to have a swim and waived my insurance liability on air as they can't get anyone to give them insurance," Mr Kerr said.
"The pool has not been chlorinated and it's not yet ready for public use, but I said I would take my chances as I occasionally swim in the Forty Foot."
Mr Kerr gave the baths a glowing review after his intrepid dip, calling it a "fabulous facility".
It is understood that the pool may be open to swimming clubs by the end of next month, but it will take longer to open it to the public.