sentences:  In 1838, after leaving the Chagos, Robert Moresby went on to survey the Saya de Malha bank.This is a vast submerged reef south-east of the Seychelles and since there is no island above the surface, the men were forced to spend many days at sea often under difficult weather conditions.Moresby could complete only part of this survey, namely the Southern Bank, for this arduous task and the accumulated fatigue from his previous surveys, took a toll on his health.