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The world ocean occupies 70 % on the earth and the average sea depth is about 4,000 m. More than 80 percent of it has not been investigated precisely and the bottom shape of the sea has not been mapped. When doing resource-searching in the future, the precise maps must be required. So, the authors have developed a drone movable around 4,000 m deep sea to measure the bottom of the ocean. It is based on spheres, which includes cameras, batteries, some sensors and controllers. It can rotate a spherical rotor sensing widely to obtain the information about the bottom of the sea. At the first step of the research, the authors have made basic experiments of the motor's performance in water. The authors have obtained the excellent results in maneuverability, temperature durability, and shock resistance of the motor.