Based on the historical Battle of Myeongnyang, it stars an ensemble cast led by Choi Min-sik as the Korean naval commander Yi Sun-sin.

[5][6][7] The film revolves around the titular Battle of Myeongnyang around 1597, which is regarded as one of legendary Joseon Admiral Yi Sun-sin's most remarkable naval victories.

[8] At the onset of the battle at their base in Haenam, the Japanese invaders under Tōdō Takatora are confident that their planned expedition to Hansong to capture King Seonjo will be rather straight forward.

However, they remain reserved over the news that Joseon's greatest admiral, Yi Sun-sin, has been restored to his former command after the disaster at Chilcheollyang, which has reduced the Korean navy to a mere dozen battle-ready ships.

One of the admirals of the Japanese Left Army, Wakizaka, first meets Kurushima and his lieutenant, Kimura, while he finishes off the remnants of a group of Joseon soldiers.

Facing an enemy force that far outnumbers them and seeing no reasonable chance of success in the inevitable clash even with one single turtle ship remaining, many consider the fight lost before it has even started.

However, the breaking point seems reached when General Bae Seol, the deserter of Chilcheollyang, burns the turtle ship and has his men try to assassinate Yi.

To seek an answer, Yi travels to the Myeongnyang Strait, an area notorious for its strong and treacherous currents, which the Japanese intend to cross on their way to Hansong.

Upon hearing that the departure of the Japanese attack fleet is imminent, Yi abandons his base and moves to Usuyeong after burning the naval facilities to the ground.

In the apparently hopeless situation, Yi commands several cannons to be fired from the rower deck's port hatches in a concentrated volley, to use their recoil to blast the ship free of its encirclement.

When the tide turns and forms a whirlpool in the middle of the channel, thus solidifying Yi's defensive position, Kurushima orders an all-out attack with the rest of his ships.

Despite the efforts of Haru and a ship loaded with black powder charges, the renewed courage of the Koreans prevails, though heavy sacrifices are made.

This was the all-time highest opening day box office in South Korea, for both a foreign and domestic film, breaking the previous record set by Kundo: Age of the Rampant.

[16][17][18][19] By August 15, The Admiral: Roaring Currents became the all-time most-watched film in South Korea, breaking the previous record held by Hollywood blockbuster Avatar (13.62 million).