How far out from coast is considered territorial waters?

According to the United Nations Convention on the Law of the Sea (UNCLOS), the maximum breadth of the territorial sea is 12 nautical miles (nm) from the baseline (usually the mean low-water line) of a coastal state. However, some countries have claimed territorial waters that extend beyond 12 nm, a practice that is not universally recognized.

The territorial sea is part of a state's sovereign territory, and a coastal state has full jurisdiction over its territorial waters, including the airspace, seabed, and subsoil. Foreign vessels are generally allowed to transit territorial waters, but they must comply with the coastal state's laws and regulations.