China is increasing the size of its Marine Surveillance service. This is one of five Chinese organizations responsible for law enforcement along the coast. The others are the Coast Guard, which is a military force that constantly patrols the coasts. The Maritime Safety Administration handles search and rescue along the coast. The Fisheries Law Enforcement Command polices fishing grounds. The Customs Service polices smuggling.
China Marine Surveillance service is the most recent of these agencies, having been established in 1998. It is actually the police force for the Chinese Oceanic Administration, which is responsible for surveying non-territorial waters that China has economic control over (the exclusive economic zones, or EEZ), and for enforcing environmental laws in its coastal waters. The new program will expand the Marine Surveillance force from 9,000 to 10,000 personnel and buy 36 new patrol boats. Marine Surveillance already has 300 boats and ten aircraft. In addition, Marine Surveillance collects and coordinates data from Marine Surveillance activities in ten large coastal cities and 170 coastal counties.
But this expansion is mostly about the EEZ, and patrolling it more frequently and aggressively. International law (the 1994 Law of the Sea treaty) recognizes the waters 22 kilometers from land as under the jurisdiction of the nation controlling the nearest land. That means ships cannot enter these "territorial waters" without permission. However, the waters 360 kilometers from land are considered the Exclusive Economic Zone (EEZ), of the nation controlling the nearest land. The EEZ owner can control who fishes there, and extracts natural resources (mostly oil and gas) from the ocean floor. But the EEZ owner cannot prohibit free passage, or the laying of pipelines and communications cables. China has already claimed that foreign ships have been conducting illegal espionage in their EEZ. But the 1994 treaty says nothing about such matters. China is simply doing what China has been doing for centuries, trying to impose its will on neighbors, or anyone venturing into what China considers areas under its control.
For the last two centuries, China has been prevented from exercising its "traditional rights" in nearby waters because of the superior power of foreign navies (first the cannon armed European sailing ships, then, in the 19th century, newly built steel warships from Japan). However, since the communist took over China 60 years ago, there have been increasingly violent attempts to reassert Chinese control over areas that have long (for centuries) been considered part of the "Middle Kingdom" (or China, as in the "center of the world").
China is particularly concerned about the nearby Spratlys, a group of some 100 islets, atolls, and reefs that total only about 5 square kilometers of land, but sprawl across some 410,000 square kilometers of the South China Sea. Set amid some of the world's most productive fishing grounds, the islands are believed to have enormous oil and gas reserves. Several nations have overlapping claims on the group. About 45 of the islands are currently occupied by small numbers of military personnel. China claims them all, but occupies only 8, Vietnam has occupied or marked 25, the Philippines 8, Malaysia 6, and Taiwan one.
China prefers to use non-military or paramilitary ships (like those of the Marine Surveillance service) to harass foreign ships it wants out of the EEZ or disputed warfare. This approach is less likely to spark an armed conflict, and makes it easier for the Chinese claim they were the victims.