IWERT, Sebald (e'-vert), Dutch navigator, born in Antwerp in 1558; died in Magellan in 1603. He became chief of staff to Simon de Cordes when the latter succeeded, on the death of Admiral Jacques, to the command of the Dutch South American exploring expedition of 1598. The expedition arrived in Buenos Ayres in December, and anchored in April, 1599, inside the Strait of Magellan, near the Penguin islands, in a bay that they named Mussel bay. A few days later they advanced 300 miles and entered a water which they named Green bay. After remaining here three months and suffering greatly from cold and sickness, they left at the end of August, and after various other adventures sailed for Antwerp in February, 1600. On 28 February, 120 miles from the continent, Iwert discovered a group of three islands which he named the Sebald islands. In 1603 he went again to Magellan, to join the expedition of Olivier de Noort, but died a few days after reaching the Penguin islands. He made a valuable chart of parts of the South American coast, and published "Relation du voyage des Amiraux Mahn et Simon de Cordes au detroit de Magellan" (Leyden, 1603, with charts).