It is generally believed, I think, that the waterways interests of the Office of Public Works were handed over to Waterways Ireland, and so indeed most of them were. However, the Office of Public Works (OPW) is still, I believe, responsible for two areas on the Shannon Estuary.
The first of them is the pier at Saleen, near Ballylongford in Co Kerry. This was one of the piers developed by the Shannon Commissioners in the 1840s. To the best of my knowledge the OPW managed to pass over responsibility for the rest of the piers but the Grand Jury (and later Kerry County Council) were not tempted to take over Saleen and it remains in the hands of the OPW.
The second is the Maigue Navigation, near Adare in Co Limerick. Although the Maigue is a tributary of the tidal Shannon, it was always treated as a separate navigation and reported on separately. What seems to have happened here is that it was forgotten after the 1920s: there was drainage work (the river is embanked, like most estuary tributaries) but the OPW’s role as a navigation authority was overlooked.
As far as I can tell — and my efforts have included pestering helpful OPW staff, to whom I am grateful — the navigation was neither formally abandoned nor passed to any other body. As the Shannon Navigation, now run by Waterways Ireland, ends at Shannon Bridge, Limerick, the Maigue would not have been transferred to its care even if its existence had been remembered.
If I were the OPW, I would even now be briefing the Office of the Parliamentary Counsel to the Government in order to get a quick Statutory Instrument declaring the Maigue to be no longer a navigation. I see no point in their spending a lot of money on the Maigue, but I would like to know what the OPW’s responsibilities are as a navigation authority.