The Karimata Strait is the wide strait

Strait

A strait or straits is a narrow, typically navigable channel of water that connects two larger, navigable bodies of water. It most commonly refers to a channel of water that lies between two land masses, but it may also refer to a navigable channel through a body of water that is otherwise not...

 that connects the South China Sea

South China Sea

The South China Sea is a marginal sea that is part of the Pacific Ocean, encompassing an area from the Singapore and Malacca Straits to the Strait of Taiwan of around...

 to the Java Sea

Java Sea

The Java Sea is a large shallow sea on the Sunda Shelf. It was formed as sea levels rose at the end of the last ice age. The Java Sea lies between the Indonesian islands of Borneo to the north, Java to the south; Sumatra to the west, and Sulawesi to the east...

, dividing the island

Island

An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...

s of Sumatra

Sumatra

Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...

 from Borneo

Borneo

Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....

 (Kalimantan), both in Indonesia

Indonesia

Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

.

The strait is about 150 km wide, as measured from the east coast of the island of Belitung

Belitung

Belitung, , is an island on the east coast of Sumatra, Indonesia in the Java Sea. The island is known for its pepper and for its tin. It was in the possession of the British from 1812 until the British ceded control of the island to the Dutch in the Anglo-Dutch Treaty of 1824...

 to the west coast of Borneo (Kalimantan). Belitung is separated from Bangka Island

Bangka Island

Bangka is an island lying east of Sumatra, Indonesia. Population 626,955. Area: c.4,600 sq mi .There is an additional small island named Pulau Bangka in northern Sulawesi, Indonesia.-Geography:...

 to the west by the much narrower Gaspar Strait

Gaspar Strait

Gaspar Strait separates Belitung and Bangka islands in Indonesia. It connects the Java Sea to the South China Sea.These straits, formed between the large islands Banca and Billiton, are generally called Gaspar Straits, after the Spanish captain from Manila, who passed through them in 1724; but...

. Bangka lies close to the east coast of Sumatra, separated from it by the Bangka Strait

Bangka Strait

Bangka Strait is a strait which separates the island of Sumatra and Bangka Island in the Java Sea, Indonesia.-See also:* Japanese cruiser Ashigara* List of straits...

. The Karimata islands

Karimata islands

The Karimata Islands are a chain of small islands off the west coast of Indonesian Borneo, the largest of which is Karimata, being about 20 km across , and situated at...

lie in the eastern part of the Karimata strait, northeast of Belitung and off-shore from the west coast of Borneo.