Nam Sang Wai is in the east of Wang Chau, Yuen Long. It is surrounded by Kam Tin River and Shan Pui River.

The place's habitats are diversed. There are geiwais and fish ponds, from which the name's 'wai' come. On the rivers are mudflats and mangroves, which attracts birds like sandpipers and Great Cormorants. Migratory birds also winter there, including the endangered Black-faced Spoonbill. There are also grasslands and reed beds. On the sides of the grasslands are Eucalyptus trees. Many citizens enjoy picnicking, dog-walking, cycling and even playing toy boats and planes.

Nam Sang Wai faces a lot of threats, however. The rivers are channelized, causing a change in wtaer flow and hence affecting organisms inside. Noises produced by visitors and industries nearby disturb birds and insects on the rivers and in the reed beds. In recent years, Henderson Land Development and KHI Holdings Group proposed a development plan of turning part of Nam Sang Wai into a residential area, and yet despite multiple alternations, the plan failed to keep its 'zero loss of wetlands' promise, and failed to make up for the ecological damages. Hence, the plan was objected by green groups. In addition, the Eucalyptus trees also experienced several fires. While the trees are themselves rather flammable, it was suspected that arsons were committed to force the passing of the plan.