Complex sentence: Captain William Nichols of Falmouth, England was the captain and co-owner of the transport vessel, the Duke William, when it sank in the North Atlantic on December 13,1758.
Split into simpler sentences: Captain William Nichols of Falmouth, England was the captain and owner of the vessel known as the Duke William. Captain Nichols was the captain of Duke William when it sank in the North Atlantic on December 13,1758.