Saltdean Lido has lost £250,000 in the past five years, its owner said
The first public meeting to discuss plans to redevelop a Grade II-listed outdoor pool in East Sussex resulted in fierce opposition from supporters.
Saltdean Lido, which was built in the 1930s, is facing closure after visitor numbers dwindled in recent years.
On Sunday, local people were outraged when leaseholder Dennis Audley revealed revised plans which includes 40 flats.
Rebecca Crook, of Save Saltdean Lido Campaign, said to lose such an iconic building to flats would be "a tragedy".
Mr Audley, who has leased the lido from Brighton and Hove City Council for the past 10 years, said the outdoor pools would be retained, with plans for an additional pool inside the complex.
He added that the apartments behind the lido building would finance the redevelopment of the site, which also included plans for a community building and library.
"We are passionately trying to keep the building in the long term, and we're open to many other ideas.
"Everyone has to realise that we have been talking to Brighton and Hove council for the last three years with various different permutations and drawings and calculations," he said.
Earlier this year, Mr Audley revealed that the art deco lido had lost more than £250,000 over five years due to a succession of poor summers.
Ms Crook said campaigners were strongly opposed to any residential development on the site.
"What we would like to see happening is investment, management into the site, and possibly looking at the options of a community interest group operating the site."
She added that although British summers were not always favourable for lidos, the campaign group would welcome a cafe, [and] other amenities and facilities for the community and visitors to the area.
"We acknowledge there has to be some kind of change on the site, and obviously things need to evolve and move with the times, but I think there's still a lot of nostalgia around lidos."
Two more public meetings on the issue take place on Monday afternoon at the community centre in Saltdean.
Dennis Audley, leaseholder of the grade II listed Saltdean Lido, said he wanted to preserve the appearance of the site