Admiral Yi set out again eastward and encountered another force around the Sacheon-Dangpo area, where he again engaged in minor skirmishes against the Japanese fleet. Yi Sunsin's fleet managed to destroy 13 large Japanese ships. It was the first battle of Admiral Yi's 2nd Campaign in the Imjin War, between Japan and Korea, when the turtle ship was first used. The fierce and sudden Korean attack shocked the Japanese. But unlike their previous poor performance at the Battle of Okpo, the Japanese soldiers fought bravely and returned fire with their arquebuses in a timely manner.

Unfortunately for the Japanese, they did not have a chance to board the Korean ships because of concentrated Korean cannon fire. Also, the turtle ship was impossible to board anyway due to iron spikes on its roof. Then, the Japanese began to panic when the turtle ship smashed into Japanese lines, firing in every direction.