Tonga Territorial Sea (12 Nautical Mile)

The territorial sea of Tonga comprises those areas of the sea having, as their inner limits, the baseline described in sections 5 and 6 of this Act and, as their outer limits, a line measured seaward from that baseline, every point of which line is distant 12 nautical miles from the nearest point of the baseline.

                                                                           Baseline of territorial sea

1. (1) Except as otherwise provided in section 6 of this Act, the baseline from which the breadth of the territorial sea of Tonga is measured shall be: (a) In the case of islands situated on atolls or of islands having fringing reefs, the low-water mark along the seaward edge of the reef; (b) In the case of islands not situated on atolls or of islands not having fringing reefs, the low-water mark along the coast of those islands. (2) For the purposes of this section, a low-tide elevation that lies wholly or partly within the breadth of sea that would be territorial sea if all low-tide elevations were disregarded for the purpose of the measurement of the breadth of the territorial sea shall be treated as an island.

https://www.un.org/depts/los/LEGISLATIONANDTREATIES/PDFFILES/TON_1989_Act.pdf

Tonga's 12 nautical mile zone was extracted from the Global Marine Regions platform (https://www.marineregions.org/) since they have not deposited formally with UNDOALOS.