I’ve already written about a Shannon lock at Athlone and a Grand Canal lock at Belmont. Now here’s a page about the sector lock leading into Kilrush marina on the Shannon estuary. Sector locks are relatively rare, but sector gates are being installed as flood defences at Spencer Dock, where the Royal Canal meets the River Liffey in Dublin, and are used at Limehouse lock on the Thames in London.
Interestingly, the Kilrush lock and the associated embankment solved problems that were identified by Commander William Mudge RN, Admiralty surveyor, in 1831: he was one of the three members of the Commission for the Improvement of the Navigation of the Shannon, and at that time the Shannon estuary steamers had to use Cappagh pier, outside Kilrush, because at low tide Kilrush had only a small creek running through it.
Nowadays, inland waterways boats going to sea often head for Kilrush, which is also one of the bases from which dolphin-watching trips are provided. There is a resident school of bottlenose dolphins in the estuary.
Irish waterways history 