High seas refers in practice to sea areas that lie beyond the territorial sea and other zones over which any coastal state exercises sovereignty, such as the territorial waters of the UK or Ireland. It is used in shipping, marine insurance, criminal jurisdiction, fisheries, environmental law and public international law.In UK and Irish law, the concept largely follows international law, particularly the United Nations Convention on the Law of the Sea (UNCLOS), under which the high seas are open to all states and not subject to the sovereignty of any one state. They begin seaward of the outer limit of the exclusive economic zone (EEZ) or, where no EEZ is claimed, beyond the territorial sea.Key legal consequences include: freedom of navigation and overflight; flag-state jurisdiction over ships; limited bases for exercising criminal or regulatory jurisdiction; and specific treaty-based obligations regarding pollution, conservation of living resources and piracy.Usage and meaning are broadly consistent across England & Wales, Scotland, Northern Ireland and Ireland, with domestic legislation in each jurisdiction incorporating or applying UNCLOS-based definitions where needed.