Not long ago, a member of my sports club noticed that I was swimming sidestroke in the pool. He was curious enough to ask how it was that a foreigner had learned 古式泳法 koshiki eiho. This was a term that I had never heard before, but he told me it’s the way samurai used to swim. The term literally means “ancient way of swimming.”
I explained to him that I had learned it long ago it from the American Red Cross when training to be a lifeguard. Swimming on your side means that you can propel yourself forward with your lower arm while using your upper arm to hold your rescue victim and keep their head above the water.
This posture has obvious military uses. Also, the fact that sidestroke is virtually splash-free makes it a stealthy way of moving through the water. This is something that not only ancient samurai but also the modern U.S. military has noticed.
The man at the pool urged me to look up koshiki eiho on the Internet. When I did, I learned the term 日本泳法 nihon eiho, which covers a wide range of ancient aquatic techniques. The best material I found is the video at the top of this post, which reveals a startling connection between synchronized swimming and martial arts. Have a look!