The Banc is a dangerous oval-shaped reef 8 km (5 mi) long and 5 km (3 mi) wide that becomes exposed only at low tides, with the exception of some rock formations in the southern part of the reef.

In the eastern part of the reef there are some sandy cays, 1 to 3 m (3 to 10 ft) in height covered with grass and small bushes.

About 20 km (12 mi) southwest of Geysir is Zélée Bank, a deep submarine feature.

France and the Comoros claim the Banc du Geyser as part of their exclusive economic zone (EEZ).

Madagascar announced its annexation in 1976, presumably because of the possibility of oil fields in the vicinity but the Banc du Geyser is controlled in fact by the French forces armées de la zone sud de l'océan Indien.