When Matsuo Koga straps on 33 pounds of armor and slips into the swimming pool, he's following a centuries-old tradition in Japan:
Traditional swimming was developed during Japan's feudal 15th and 16th Centuries, when feared samurai swordsmen roamed the country enforcing their masters' will.
Part survival technique -- there were times when a warrior just had to swim for it, boots and all -- and part aesthetic performance, traditional swimming now has its place in the pantheon of Japanese martial arts.
And like all martial arts, its adherents say it has real-life applications.
"The primary purpose of this kind of swimming is to acquire practical skills for swimming in a real environment," said Tadao Koga, Mutsuo's father and the grand master of the Kobori school, one of twelve recognised by the Japan Swimming Federation.
"If you can swim fast using Western strokes, that doesn't mean you can survive in a natural environment," said Koga, 67.