Selat Siberut, between Pulau Bojo and Pulau Siberut, is about 21 miles wide.
Selat Siberut is the passage usually taken by vessels bound to Teluk Bayur from N.

Low-powered vessels from the Indian Ocean bound to Selat Sunda between May and september, and all vessels bound N from Selat Sunda between November and March, use this passage.

There is generally a long line of surf on the shores of the strait, particularly on its N and W portions. In the E portion, and under the Pulau Siberut shore, there is shelter from the sea which causes heavy surf on the N shore, where all the dangers lie within the 5.5m line.

Vessels approaching Selat Siberut from the W should steer to pass about 2 miles S of the W point of Pulau Tanahbala, and will sight Pulau Bodjo with its lighthouse.

The best course is to pass between Pulau Bodjo and Makasser Reef, which is clear of all danger; the reef is nearly always to be seen by the breakers.

The island should be passed at a distance of 2 miles, steering about 090°, until Tanjung Sigep bears 155°, when a course may be shaped for the desired port.

Vessels approaching Selat Siberut from the W should steer to pass about 2 miles S of the W point of Pulau Tanahbala, and will sight Pulau Bodjo with its lighthouse.

The best course is to pass between Pulau Bodjo and Makasser Reef, which is clear of all danger; the reef is nearly always to be seen by the breakers.

Winds—Weather

From November to May, when the Northeast Monsoon prevails S of the Equator, the weather is fine in Selat Siberut, with light S and SW winds. The wind is rarely stronger than force 2; in March and April strong W squalls lasting about 10 minutes may be experienced. In the other months of the monsoon rain, squalls with little wind may be expected.

If the wind shifts to S during the Southwest Monsoon period, which usually occurs between June and September, hard NW and W winds prevail in Selat Siberut, accompanied by heavy squalls.

Tides—Currents

The tidal currents are reported to be irregular.
Sometimes a W set is experienced for several successive days; at other times, an E set is experienced, with the latter being generally the weaker.

After a few days of light winds the currents turn at about HW and LW. The strongest currents are found close to the shores, where, N of Tanjung Sigep (0°54'S., 98°54'E.), the N extremity of Pulau Siberut, and between Pulau Bodjo and Pulau Tanahbala, they sometimes attain a rate of from 2 to 3 knots. In the latter vicinity the flood sets ENE and the ebb WSW.