Speakers Bank is a large coral atoll structure in the Northwestern part of the Chagos Archipelago. It is the northernmost feature of the archipelago, located at (04°55′S72°20′E), 22 km Northwest of Blenheim Reef and is 44 km Northeast-Southwest, and 24 km wide. The total area is 582 km², most of which is water. Most of the rim of the reef is between 5.5 and 14.5 metres below water. In the south, near the southwest edge, there are some coral heads at 05°04'S, 072°16'E, 0.5 metres of which are dry during low tide, and over which the sea breaks heavily during the southeast trade winds. In the Northeast, at 04°47'S, 072°26'E, there are a number of drying cays, the biggest of which, Big Speaker Reef, just reaches the high water mark.