territorial sea boundary

The territorial sea reaches twelve nautical miles out from the baseline. Inside it the country holds full sovereignty, so the water, the seabed beneath it and the airspace above it are part of the state.

Foreign vessels keep a right of innocent passage through it, which is the one substantial limit on that sovereignty.

The width is set by the Convention on the Law of the Sea, article 3. Where two countries lie closer than twice the limit, the boundary is a median line or a negotiated one instead.