清代將接近大陸海岸和島岸的海域劃分成三個部分: 一是內洋, 這部分海域由於靠近大陸海岸或島岸, 以一些小島為標誌, 由沿岸州縣和水師官兵共同負責管轄;二是大洋、深水洋或黑水洋, 這部分海域無邊無際, "非中土所轄", 類似於現代的公海;三是介於二者之間的一條洋面, 清人稱其為外洋, 這部分海域通常以距離中國海岸、島岸最遠的島礁為標誌, 由於超出了文官的管轄能力, 主要委派水師官兵來巡閱會哨。

The Qing government divided the waters approaching the continental coasts and the island coasts into three parts. The first part was the" inner seas. "This area was marked by some small islands because it was close to continental or island coasts, so normally the coastal prefectures and counties co-administered it with naval officials. The second part was the "big seas," including "deep-water" or "black-water" seas which were immense and boundless. This part was not China’s territory, and it is similar to the modern "high seas." The third part consisted of the seas between the first two parts; the Qing called them the "outer seas." The boundary of this part was generally marked by the reefs furthest from Chinese coastal territories or islands. Because this part of the seas exceeded the ability of civil officials to administer, the Qing government primarily sent the navy to patrol them.