In this study, a ray-mimic underwater robot was designed and implemented. The robot is propelled by its pectoral fins. The robot is equipped with IR sensors and an image sensor for obstacle avoidance and object racking, respectively. Its specific gravity is adjusted by two water storage tanks and its center of gravity is controlled by two screw-rods. The image data is processed on board using a DSP chip installed in the robot and motion control is achieved by PIC16F877 micro-controllers. Obtained data are also sent to its user via wireless communications so that real time performance can be accomplished. Experimental results show that the robot achieves its designed functions successfully.