The only indoor swimming venue for naturist swimming is Crumlin pool in Dublin which is organised by the Irish Naturist association (INA). I think there is a swim there once a month. They do not permit unmarried men to join this activity.
And that's it, I'm afraid.
Unlike the Netherlands where about half of the public pools have designated nude swimming times, open to all. Similar situation in Germany and Scandinavia and, to a lesser extent, France.
For the record the Vico Road bathing area still attracts many nude swimmers, especially on good weather days. I've used it a few times.