Landsat of Victory Bank.    The shallowest parts are 5 m deep, but the structure still has a clear atoll form.  In 1979, the 'lagoon' had good coral cover, as did the rim.   Landsat 2 multi-spectral scanner, 1st March 1978.  Left: False colour composite. Right: unsupervised classification, using bands 4, 5, 6 and 'z' which is a depth invariant band. 
(ref: Sheppard, Seaward, Klaus and Topp, 1999. The Chagos Archipelago: An introduction.  In: Sheppard and Seaward (eds) Ecology of The Chagos Archipelago.  Linnean Society Occassional Publications, London. pp 1-22.)
