Complex sentence: As a result of sailing and merchant activity, the island's economy quickly picked up but declined again during the late 19th century and especially after the opening of the Corinth Canal in 1904 and the First World War at the beginning of the 20th century.
Split into simpler sentences: As a result of sailing and merchant activity, the island's economy improved. It declined again during the late 19th century; especially after the opening of the Corinth Canal in 1904 and the First World War at the beginning of the 20th century.