Many aqua robots are in practical use to investigate various aquatic animals in sea. However, their size is large and they make a noise and a large water flow because the impellent is obtained by rotating screw propeller. In a word, live fishes fear the aqua robot. Therefore, small fish robot of fin drive type becomes useful. When the fish robot swims in the vicinity of the water surface in shallow area where the bottom is seen from the water surface, the electric wave can be used. In this study, we have made a small fish robot with the ability to observe target objects such as live fish. In addition, we have tried to make the fish robot follow the target object autonomously.