Hong Kong is a Special Administrative Region (SAR) of China and has ~1,651 km² of territorial waters and a relatively long coastline of 1,189 km (equivalent to the coastline of England and Wales), largely due to the presence of over 260 islands. Located at 22° N and 114° E, Hong Kong lies just within the tropics and is influenced by a strongly seasonal climate as a result of changes between the northeast and southeast monsoons, which create a climate of cold, dry and almost temperate winters and hot, wet, tropical summers. Associated with the monsoonal climate, Hong Kong experiences seasonal changes in the dominance of three ocean currents, the Taiwan, Hainan and Kuroshio currents. Hong Kong's geographic location and seasonal shifts in monsoons and ocean currents therefore create an extremely dynamic environment and contribute to the mix of tropical and temperate flora and fauna found in Hong Kong.

The western waters of Hong Kong, under the influence of the Pearl River discharge from mainland China, are estuarine and as a result Hong Kong's waters can be divided into three hydrographic zones: the estuarine west, oceanic east and a central transition zone. Hong Kong waters, as elsewhere, can also be divided into the intertidal, sub-littoral and continental shelf zones. The intertidal zone is extremely diverse, with rocky shores focused on granitic and volcanic promontories that are interspersed with deep wave-cut bays. There is also a rich variety of sandy and muddy shores in deeply cut inlets of Hong Kong, with the most protected areas supporting mangrove stands. In the lower shore to sub-littoral, soft shores can support seagrasses and coral communities can be found in rocky sub-littoral areas, whereas the continental shelf is mainly comprised of muddy sands. The influence of the monsoonal climate, complex geology, seasonal variation in oceanic currents, proximity to the Pearl River, long drowned coastline, and diverse ecological habitats all interact to influence and mould the highly diverse marine biota in Hong Kong.

This work was funded by the Environment and Conservation Fund (ECF) of the Hong Kong SAR Government and led by The Swire Institute of Marine Science, The University of Hong Kong. The database has been checked by taxonomic experts of the World Register of Marine Species (WoRMS) as a procedure of quality assurance.