Successive feudal lords of the Higo Clan encouraged swimming for military purposes. During the Hoei Era (1704〜１１) Muraoka Idaiyu, a retainer of the Higo Clan developed secret swimming techniques. His son, Kobori Chojun, following in his father's footsteps, became a swimming instructor for clan retainers until his death in 1771. In the 6th year of the Horeki Era (1756), in order to preserve his father's swimming techniques for posterity, he published "Tosuiketsu, Suiba Senkin Hen, and Suiren Hayagaten". These are the oldest treatises on swimming in Japan. Kobori Seizaemon, the 5th generation swimming master (counting from Chojun), developed these techniques further and gave himself the title of Suioh. He compiled a book on swimming methods. The 6th generation master, Saruki Sona, sent his younger brothers to different places as instructors: Kobori Heishichi to Gakushuin, Jo Yoshizane to the Kyoto Butoku-kai, Soke Nishimura to Iwakuni, and his best pupil to Nagasaki. In addition, he published a modern group-training manual, "Kobori-ryu Treading Water Textbook," which spread nationwide and still exists in Kyoto, Gakushuin, and Nagasaki. 　It is characterized by water treading skills, and includes foot strikes, hand carries, overarm strokes, quick overarm strokes, vertical swimming, diving, floating, gozen-swimming, and floating-swimming.