Pulau-Pulau Aruah (Aruah Islands) is composed of two groups of small islands and some off-lying rocks which are located on a bank with depths of less than 20m. The S end of the bank joins an extensive mud bank lying adjacent to the Sumatera coast.

Batu Utara (2°55'N., 100°36'E.), the northernmost islet of the group, is about 4.6m high and has a reef extending N.
Batu Byms (Byms Rock) (2°54'N., 100°35'E.), awash, lies about 2 miles SSW of Batu Utara. The charted position is approximate.
Pulau Jemur (2°53'N., 100°34'E.), 22m high, flat, and treecovered, stands about 3 miles SSW of Batu Utara.

Kalironggo Islet stands on a reef about 0.3 mile NE of Pulau Jemur, and a drying reef lies about 0.5 mile farther NE.
A round islet, about 50m in diameter and surrounded by a reef about the same distance in width, stands 0.3 mile SE of Pulau Jemur Light.

A group of five islets lie on a bank, with depths of less than 10m, which lies a little over 0.5 mile WSW of Pulau Jemur and extends in a NNW and SSE direction.

Tokong Mas (2°53'N., 100°33'E.), the northernmost of the group, is 31m high, several drying reefs lie within 0.4 mile N of Tokong Mas. Pasir Pandan, 20m high, and Sarong Alang, 27m high, stand on the same reef S of Tokong Mas.

Labuan Bilik, 20m high, stands about 137m SE of Sarong Alang.
Tokong Sipotjong lies about 0.3 mile SSE of Labuan Bilik.
A drying reef lies between the two.

Batu Berlayer (2°52'N., 100°38'E.), a group of six low rocks, surrounded by a reef, lies about 3 miles E of Pulau Jemur.
Half Tide Rock (2°52'N., 100°40'E.), which dries 2.4m and is steep-to, lies about 2 miles E of Batu Berlayer.
Batu Mandi (2°52'N., 100°41'E.), 2m high and steep-to, lies 7 miles E of Pulau Jemur.

Tokong Simbang (2°48'N., 100°38'E.), 38m high to the tops of the trees, is precipitous and the highest of the Kepulauan Aruah Group. This islet lies about 6 miles SE of Pulau Jemur and can be seen on a clear day for a distance of 15 miles.
There are several rocky islets around it. Tokong, 9m high, stands 1.5 miles SSW of Tokong Simbang.

The large shoal area which extends about 30 miles N fromthe entrance of the Sungai Rokan to within 2.5 miles S ofTokong.

Tides—Currents

The SE current off Pulau-Pulau Aruah begins about 4 to 5 hours before HW along the coast and runs from 1 to 2 hours after, at a rate of about 2 knots at springs.

The NW current has a rate of about 3 knots. At neaps, the SE current being opposed by the prevailing NW current results in a very weak set in either direction.