According to military sources cited by media, South Korea is expected to conduct underwater tests of an indigenous submarine-launched ballistic missile (SLBM) in 2021, having concluded ground tests.
Yonhap News Agency cited a military source saying that "related agencies wrapped up ejection tests of the missile on the ground last year. They are to move on to the next stage of conducting underwater test launches."
The source continues that it has not been decided yet on the time and the platform on which the underwar tests will be conducted, adding that it could either be a submersible test barge or a submarine.
The agency reported that the South Korean Ministry of Defence refused to confirm those counts, and simply said, "Our military has secured advanced high-power assets, such as missiles, to support peace on the Korean Peninsula, and will continue to develop them."