China admitted that the submerged submarine the Japanese navy has been tracking off the coast of Okinawa was, indeed, a Chinese boat. The Japanese had always insisted that the sub was Chinese. Apparently, American P-3 patrol aircraft, operating from Guam, were the first to pick up the location of the Chinese sub on November 9th, and then turned the tracking over to the Japanese navy. It was American technology that confirmed the identification of the sub. During the Cold War, the United States developed techniques for identifying individual submarines according to their shape, and by the noises they made. The American navy maintains electronic databases of submarines "signatures." The same technique apparently also worked for large whales.
China has apologized for the incident, which had their boat inside Japanese territorial waters for a short period of time. China said the cause was a navigational accident. China has been sending its subs to see more often over the last few years, in order to raise the skill levels of the crews.