Medical officers from US Navy hospital ship Mercy learn Tai chi from Chinese counterparts at the Chinese People's Liberation Army Navy hospital ship Peace Ark. Peace Ark and the US Navy ship Mercy have conducted extensive exchanges since the Rim of the Pacific exercise (RIMPAC) started on June 26 near the Hawaiian Islands. They are the first hospital ships participating in RIMPAC since the world's largest naval drill began in 1971. Photo by Ju Zhenhua / CHINA DAILY