North Korean leader Kim Jong-un watched a rare swimming drill of Navy officers, the North's official Korean Central News Agency reported on Wednesday.
In an apparent effort to bring officers into line, Kim was quoted as saying, "Commanders need to become fighters in order for the whole military to fight well."
Kim has ramped up a campaign to tighten discipline amongst high-ranking officers. In March, Kim ordered Army officers to carry out shooting drills and watched them at it.
In May, he ordered O Kum-chol, the 67-year-old vice chief of the Army's General Staff, to fly a fighter jet.