Natuna Sea
The Natuna Sea () is an extensive shallow sea located around Natuna Regency extended south to Lingga and Tambelan Archipelago in the Riau Islands province, further south of Bangka Belitung Islands, Indonesia. Most of the sea is located within Indonesian territorial waters, and geologically is the part of Sunda Shelf. This sea is bordering South China Sea to the north and northeast, Karimata Strait to the southeast, and Strait of Singapore to the west. 

The International Hydrographic Organization (IHO), in its Limits of Oceans and Seas, 3rd edition (1953), does not list a Natuna Sea. Instead, the area encompassed by the Natuna Sea is considered the southern portion of the South China Sea. The 1986 draft of the IHO's Limits of Oceans and Seas proposed the Natuna Sea, which extends south from the Natuna and Anambas Islands to the Belitung Islands. However, the 1986 draft edition was never approved.

Extent
The chains of Anambas and Natuna Islands created arch that connects southeastern tip of Malay peninsula to western tip of Borneo. This creates the northern boundary of Natuna Sea. While on the south, the southeast coast of Sumatra, the Lingga Islands, Bangka and Belitung islands creates its southern boundary and its opening to Karimata Strait and Java Sea.

Geography
Just like South China Sea, Natuna Sea is a marginal part of Pacific.
Natuna sea contains numbers of archipelagos, including:
 Natuna Islands in Natuna Regency
 Greater Natuna Archipelago in Natuna Regency
 South Natuna Archipelago in Natuna Regency
 Anambas Archipelago in Anambas Islands Regency
 Lingga Archipelago in Lingga Regency
 Tambelan Archipelago in Bintan Regency
 Riau Archipelago
All of these archipelagos are administrated within Riau Islands province.

North Natuna Sea

In July 2017, Indonesia renamed the northern reaches of its exclusive economic zone in the South China Sea as the "North Natuna Sea", which is located north of the Indonesian Natuna Regency, bordering southern Vietnam's exclusive economic zone. The North Natuna Sea is located between the Natuna Islands and Cape Cà Mau on the southern tip of the Mekong Delta in Vietnam.