Yi led a flotilla of 40 ships alongside Yi Sun Sin and Won Gyun during the Battle of Tanghangpo, Battle of Hansan-do, Battle of Angolpo, the First Battle of Busan Harbor (1592), and the Battle of Unchong. He received a promotion and special recognition for having a major role in the destruction of a Japanese flotilla during the Battle of Hansan-do.
The order to attack the Japanese near Busan originated from King Seonjo himself. The attack on an entrenched Japanese force was viewed by the Korean navy and even some within the government as a suicide mission—in fact, Yi Sun Sin was removed largely for defying this attack order. Factionalism in Seonjo's court pushed Yi Sun Sin's replacement, an equally unenthusiastic Won Gyun, to go forward with the order. On August 20, 1597, an inept Won Gyun led the 200 ship flotilla on an extended row and into a Japanese ambush of 1,000 ships laying off the coast of Cholyong-do. It was now nighttime and Won Kyun and Yi Eok-gi, both unaccustomed to fighting at night, were forced to retreat their exhausted crews multiple times as the Japanese tried to close their trap shut. The commanders fled to the Chilcheollyang Strait where they were later crushed by the advancing Japanese navy. As the Japanese destroyed the Korean fleet, Won Gyun fled, but Yi Eok-gi refused to leave, fighting on until he finally jumped into the waters to his death.