Except in three places, on the east coast the baseline from which the breadth of the territorial sea and the other maritime zones of the State is measured is the 'normal' baseline, being the low-water line along the coast of the mainland and of offshore islands, and the low-water line on any low-tide elevation located within 12 nautical miles of the mainland or of any off-shore island. The islands and low tide elevations concerned are Rockabill, Lambay Island, Ireland’s Eye, Blackwater Bank and Tuskar Rock.
The three exceptions to the use of the normal baseline on the east coast are bay closing lines drawn between the natural entrance points to Dundalk and Dublin Bays and Wexford Harbour, which serve as the baselines in the places concerned. These closing lines have operated at common law since the foundation of the State. For the avoidance of doubt the Government recently prescribed them by Order under s. 85 of the 2006 Sea Fisheries and Maritime Jurisdiction Act (S.I. No. 155/2019 - Maritime Jurisdiction (Bay Closing Lines) Order 2019).
In international law, where a coastline is deeply indented and cut into, or if there is a fringe of islands along the coast in its immediate vicinity, a State may draw straight baselines joining appropriate headlands or islands. This has been done for the west and south coasts, which meet the relevant criteria.
I will arrange for an illustrative map of the State’s baselines, together with the outer limits of the territorial sea from which they are measured, to be furnished to the Deputy.