Classical Japanese swimming, also known as Nihon Eiho, is composed of several centuries-old aquatic activities, which include writing calligraphy while treading water and swimming in a 40-pound suit of armor.

The sport, with 28 schools recognized by the Japanese Swimming Federation, traces its origins back to Japan’s Warring States period from the middle of the 15th century to the beginning of the 17th century.

Maritime battles between feudal clans often ended with samurai thrown off deck and vulnerable to either attack or drowning due to the weight of their defensive gear. The martial art of suijutsu (combative swimming) was developed to turn the tide of naval engagements. During training, samurai practiced katchu gozen oyogi (full armor swimming) and tachi-oyogi (standing swimming) with their hands held above the surface. Keeping their hands dry, the warriors would hold an ink brush and a scroll of paper to inscribe messages while staying afloat.

Surprisingly, the aqua-based calligraphy had a crucial connection to combat effectiveness. Practicing their fine motor movements above water, the samurai could eventually replace the brush and paper with a musket, which could only be fired if the black powder remained dry.

In addition to weapons, contemporary swimmers wield less dangerous objects to sharpen their dexterity, including fans, banners, and umbrellas. Other Nihon Eiho strokes can be performed without equipment.

Though long abandoned by military tacticians, these time-honored techniques are kept alive by classical Japanese swimmers. Watch below to learn more.