A €15 million heated sea pool on the River Liffey has been described as "unnecessary".
The proposal from the city council also includes sauna, yoga and cafe facilities.
It would see an outdoor swimming pool built from a modified steel barge that would be 50 metres long and 12 to 15 metres wide.
Following a feasibility study, an area on the Liffey adjacent to the planned reception building for the George’s Dock White Water facility was selected as the most suitable location.
Dublin city council says it would develop Custom House Quay into a hub for water based recreational activity in the city.
Local councillor Christy Burke says the money would be better spent on things like housing and childcare;
"Remember you will have the white water raft going in there on the docklands, you do have the River Liffey that young people swim in, you do have baths on Sean McDermott Street and there are many many activities that can be put to use without spending 15 million."
Sinn Féin councillor Janice Boylan says it's a pool for "bankers and tourists";
"I welcome extra investment for recreational facilities. But €15 million for a novelty swimming pool in the River Liffey is a non-runner. Especially when communities across Dublin are crying out for basic sports and recreation facilities."
However Alan Robinson, CEO of the Docklands Business Forum, has welcomed the project. He says it will develop an underutilised area, creating employment;
"I think its a good use of docklands maritime heritage, it will create activity and life and vibrancy in the area outside business hours and at weekends and it will also create jobs and accessible jobs for local people."