Brunei, Malaysia and Taiwan also claim all or part of the sea.

China is hardly the only party with something to lose from a threat to shipping. Most commercial vessels in the South China Sea take raw materials to East Asia, with Malacca-Spratly traffic carrying largely crude oil, liquefied natural gas and iron ore, GlobalSecurity.org says. Japan, South Korea and Taiwan are the major takers of liquefied natural gas transported through the South China Sea.

Chen Yi-Lee, marine transport analyst with SinoPac Securities in Taipei, says keeping ship traffic safe is a matter of logic for all six claimants. "They won't bother commercial activities that would affect themselves," she says.

Still, the question is whether a naval clash, possibly set off by competing offshore oil rigs or ever-aggressive fishing vessels, might accidentally net an innocent container ship or whether a captain miscalculates and strays too close to a particularly sensitive sea region such as the Paracel or Spratly islands.

A few shippers have rerouted vessels along the east coast of the Philippines to keep safe, but most have stuck to their usual lanes. Vessels from Taiwan scoot through unscathed partly by flying a disinterested flag, that of Panama for example, which also allows them to hire foreign deckhands.

The more aggressive shippers include China Cosco Holdings Co. Ltd. (1919.HK). Its total transportation volume was 5.2 million tons in the first half of 2012, up 23.5% year-on-year.

Evergreen Marine (2603.TW), the world's fourth-largest marine shipper, has made no changes. "Our crew will stay alert when sailing through this region," says Evergreen publicist John Chen in Taipei. "Unless the disputes escalate into military activities, there is no need to reroute the service strings."

But Pacific Basin Shipping (2343.HK), a major dry bulk mover for Asia, declined to comment on the movements of its 210 vessels, which must move about the South China Sea from its home base of Hong Kong.

The likes of American President Lines, part of Neptune Orient Lines (NO3.SI) and the world No. 7 shipper, and Maersk Line (MAERSK-B.CO) should also be sheltered from the dispute as they pass ships through the South China Sea, leaving their share prices untouched.

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