1842年，隨著中英〈南京條約〉的簽訂，中外往來進入五口通商的新階段，英人考量水文認知對船艦航行的重要性與必要性，在鴉片戰爭結束後不久，即派遣英國海軍積極調查、蒐集和彙整中國東南沿海水文資訊，尤其是香港至上海之間的海域，直到1857年英法聯軍之前。此一時期皇家海軍調查的主要目標之一為對五口之間沿海地貌以及海洋水文現象的理解與掌握，故本文將聚焦於此，梳理、分析在這段時期中不同階段，皇家海軍對香港至上海之間不同區域海岸線的認知進展，以及對於各類海洋水文現象之觀測與歸納。此外，也探究英人如何將調查、歸納所得的水文資訊造一步運用於「航行指引」（sailing directions)、航線籌畫與開埠選擇等實際廣面上。

With the Treaty of Nanjing signed in 1842, trade relations between Ch’ing Empire and the West entered a new stage of the so-called “Period of the Five Treaty Ports.” The British became aware of the importance of and need for hydrographic knowledges in navigating merchant ships and Royal Navy. After the end of Opium War, the British dispatched her Royal Navy actively and systematically to collect hydrographic information of the southeast coastal line of China, especially the waters from Hong Kong to Shanghai. The activity lasted until the eve of the Second Opium War in 1857. During this period, one of the major investigation goals was to have thorough understanding of the coastal landscape and conditions of marine hydrology. This article thus explores the course how the British Royal Navy built up her research on the intended information of different regions on the coastal line between Hong Kong and Shanghai. Besides, it shows how the British applied further the collected hydrographic information on her engagement of the planning of sailing passage and the choice of opening treaty ports.