Zmajević had great success in maritime battles against Sweden, against whom Russia fought the Great Northern War for supremacy on Baltic Sea. He captured seven smaller Swedish galleys in the 1714 Battle of Gangut, and his fleet fought a minor Swedish force at Grengam in 1720, in the last naval battle of the Great Northern War. As a result of Zmajević's victory, Peter the Great sent some of his young officers (boyars) to the town of Perast in Boka in order to study maritime science there. He was subsequently promoted to the rank of vice admiral and put in charge for building the river fleet of the Don. In 1725, he was given the honor of carrying the emperor's crown at the funeral of Peter the Great. Tsar's successor, Catherine I of Russia, decorated Zmajević with the Order of Alexander Nevsky, and in 1727 he was awarded the ultimate rank of admiral.