Vietnam is located on the eastern margin of the Indochinese peninsula and occupies about 331,211.6 square kilometers, of which about 25% was under cultivation in 1987. It borders the Gulf of Tonkin, Gulf of Thailand, and Pacific Ocean, along with China, Laos, and Cambodia. The elongated roughly "S" shaped country has a north-to-south distance of and is about wide at the narrowest point. With a coastline of , excluding islands, Vietnam claims as the limit of its territorial waters, an additional as a contiguous customs and security zone. It has an exclusive economic zone of with .