Under Article 13 of the United Nations Convention on the Law of the Sea (UNCLOS), a low-tide elevation (LTE) is defined as a naturally formed area of land surrounded by and above water at low tide but submerged at high tide. The legal classification of LTEs creates a critical distinction in maritime boundary disputes. If a low-tide elevation is situated wholly at a distance exceeding the breadth of the territorial sea from the mainland or an island, it possesses no territorial sea of its own.
It generates no maritime zones, meaning no territorial sea, exclusive economic zone (EEZ), or continental shelf can originate from it. However, if an LTE falls within the territorial sea of a mainland or an island, its low-water line may be used as the baseline for measuring the breadth of the territorial sea. This rule prevents states from claiming vast swathes of ocean by building structures on naturally submerged features or asserting sovereignty over reefs that disappear twice a day.
The legal logic was famously affirmed in the 2016 South China Sea Arbitration between the Philippines and China, where the Permanent Court of Arbitration ruled that feature-by-feature evaluations must determine whether features are naturally above water at high tide. Submerged reefs and low-tide elevations, even if heavily augmented by artificial island construction, remain legally incapable of generating entitlement to a 12-nautical-mile territorial sea. Thus, maritime entitlement stems strictly from natural high-tide status.