Based on an analysis of remote sensing data, including aerial photographs and satellite images, as well as ancient maps, locations of ancient rivers, which were waterways connecting areas in Chau Doc and Oc Eo - Ba The to the bay of Rach Gia - Ha Tien, have been identified. Some ancient canals in the area of Oc Eo have been also specified as essential transport routes connecting the centre of Oc Eo - Ba The to other residential areas in Long Xuyen Quadrangle. Having exploited and improved available natural streams, in the period of Oc Eo culture, local people created a system of canals, which contributed significantly to socio-economic and cultural activities in the kingdom of Funan. In addition, the research findings have also identified ancient coastal estuaries in the archaeological site of Nen Chua, proving the existence of an important seaport on the coastal trade route in Southeast Asia.