Dolgorae-class submarine

The Dolgorae-class submarine (Hangul: 돌고래급 잠수정) was a type of midget submarine designed and acquired for the Republic of Korea Navy. All three units are now retired.
These midget submarines were the first South Korean submarines of any type. They were acquired primarily to obtain initial experience with the basics of operating a submarine force. The secondary mission to train surface ASW ships in the detection of North Korean midget submarines.
Replacement.
In November 2011, South Korea unveiled plans for a new mini-sub designated KSS-500A. In September 2015, "Jane's.com" reported that Hyundai Heavy Industries started construction of a single long HDS-400 mini submarine for an unnamed naval customer.
Ships in the class.
In November 2017, one Dolgorae-class submarine was opened as a museum ship in the new Seoul Battleship Park beside the Han River in western Seoul.