Borneo is surrounded by the South China Sea to the north and northwest, the Sulu Sea to the northeast, the Celebes Sea and the Makassar Strait to the east, and the Java Sea and Karimata Strait to the south. To the west of Borneo are the Malay Peninsula and Sumatra.he sovereign state of Brunei, located on the north coast, comprises about 1% of Borneo's land area. Antipodal to an area of Amazon rainforest, Borneo is itself home to one of the oldest rainforests in the world.