One afternoon, after Master Shimabuku had finished teaching a class, he fell asleep on the water tank in his courtyard. He had a dream that a man came into the courtyard and challenged him to fight.
Shimabuku refused. He held out his open left hand and closed right fist. This hand positioning can be found at the beginning of each of our katas. The open hand symbolizes peace and the fist represents power.
The man then put a ring of fire around Shimabuku. Shimabuku used the water from the tank to put out the fire.
Master Shimabuku's dream ended there. The next day he went to the city of Naha to shop. He saw in a store window a picture of Mizu Gami, a Shinto water goddess. Her hands were in the same position as Shimabuku's had been in the dream.
When Arsenio Advincula, one of Shimabuku's students, designed a patch for Master Shimabuku, he put Mizu Gami on it for this reason.