This year, "Fish Finder Day" was established. Furuno Electric Co., Ltd. in Nishinomiya City, Japan, was the first company in the world to commercialize and sell fishfinders. The company applied to the Japan Anniversary Association for recognition of December 3, the anniversary of the company's founding, as "Fishfinder Day," and the application was accepted.
（https://www.furuno.co.jp/news/general/general_category.html?itemid=1098&dispmid=1017）
We would like to celebrate "Fishfinder Day" with you because we are studying the use of fishfinders and sonar, which use ultrasonic waves to look through the ocean. Here, I would like to write about fishfinders in a rambling manner.
