The turtle ship is a new battle ship made through the innovation than invention with the conventional battle ship of the panokseon with the steel plate on the cover and attached with the dragon head. Yi sun-shin who was the Jeolla Jwasusa improved the turtle ship existed from the time of King Taejong and manufactured three turtle ships at the main quarter, Bangdapjin, and Suncheonbu for shipbuilding plants. Thereafter, after moving the main quarter to Hansando, he built two more of the ship, totalling five turtle ships for the Joseon naval force.
There is no dispute among the scholars that the turtle ship was generally a panokseon with the roof on top and it uses the row of Korean style like other traditional ships in Korea, but there are still different opinions on the concrete structure of a1.
In relation to the structure of the turtle ship, the 『Hangrok』 of Lee Bun described in details for the turtle ship by saying that,
In the meantime, the 『Entire Collection of Chungmugong』 has the detailed record of the structure of the turtle ship in Tongjeyoung including the turtle ship that Yi sun-shin built.
Comprehensively, the appearance of the turtle ship that Yi sun-shin built had the dragon head on the front, and six guns each on both sides. And the upper cover had the path in + shape. The interior structure was in two-story (3-story) divided for beneath the ship and above the deck with the first floor as the spear and suites and others, and the second floor above the deck with the captain's room and rowing persons and combat soldiers. The reason for the cover on the turtle ship was to protect all screw in close combat, and it is covered with the steel poles to block off the enemy soldiers to come on to the turtle ship.
The turtle ship that had restored was manufactured on the basis of the a1 of the Jeolla Jwasuyoung recorded on the 『Entire Collection of Chungmugong』.
For the excellent characteristics of the a1 as a battle ship, it would protect the combat soldiers inside and it had the powerful guns as well as the defensive strength. The turtle ship jumped into the middle of the battles in the fleet and used the canons to scattered the arrangement of the Japanese battle ship, and for this purpose, the turtle ship was manufactured with sturdy materials, and in order to protect the crews from the penetration of the enemy, the plate was set with the sharp drills. Also, there were a total of 14 guns on the sides and the front and back to attack under the situation where the a1 was surrounded by the enemy ships.
In particular, reading the 《Nanjung Ilgi》, the mouth of the turtle head had the canon that it was possible to attach with the canon from the front side. And, the plate cover was made with the plate sheet that it had outstanding defense and the turtle ship could make any movement it wanted and used its guns to destroy and used its head to break down the enemy ships even at the close encounters. In this aspect, it was perhaps like a tank on the sea.
There are on-going disputes in many aspects, but it is clear that the turtle ship was the frontline ship along with the panokseons for the Joseon naval force during the Imjin War, and it had the critical role in destroying the Japanese invaders from Sacheon Battle to the Battle of Hansando, Busan Battle and others battles. In particular, these turtle ships had the cheonja chongtong, jija chongtong and other large guns to exercise powerful capability to attack with the fire arms as the basis for unyielding victories. Thereafter, the importance of the turtle ship was growing larger and larger. The turtle ships were five by the time of King Sukjong and it was increased to 14 ships in 1746 (the 22nd year of King Youngjo), and 40 ships in 1782 (the 6th year of King Jeongjo). Currently, there are many screen-fold like drawings for the training scenes of the s3 as the stories are handed down. Thereafter, the number of the turtle ship began to decline that there were 30 ships in 1809 (the 9th year of King Sunjo) and 18 ships in 1817.
In the meantime, there was an assertion that the turtle ship was existed up to the time of King Gojong that we may expect to have new discovery of relevant data.