A reef of coral and sand, S of the island's E end, fronts the shore to a distance of 0.2 to 0.3 mile; its S portion forms the N side of Pedissa Strait, the narrow channel between Pulau Tandjung Sau and the Ngenang Islands.
A reef, with a depth of 2m, lies 1.5 miles SE of Pulau Tandjung Sau Light. The reef is marked on its E side by a buoy.
Pulau Sau (Saoe) lies on the NE part of the reef that surrounds Pulau Tandjung Sau; there is a conspicuous red patch on the E side of the island. A flat, with 3.6 to 4.6m of water, extends about 0.5 mile NW of the island.