A cargo ship is supposed to move cargo. U.S. officials now say some Chinese vessels may be doing a lot more than that.Reporting this week says the giant state-linked shipping company COSCO has been accused by U.S. officials of using concealed equipment to collect intelligence for Beijing.That does not mean every ship is a spy ship. China rejects the accusation. But it does raise a brutal question about how much critical American infrastructure is being watched from just offshore.Ports, rail hubs, power systems, military bases, shipping lanes. The country runs through places that can be seen from the water. If a foreign government can quietly collect the data, it does not need a Hollywood spy movie to get it.The container is the perfect cover. Nobody looks twice at a cargo ship. That may be exactly the point.