As mobile robots decrease in size so does their ability to traverse rough terrain. New forms of locomotion beyond the basic wheel are being explored to overcome this fault. This paper expands on the mechanical design of a previous robot with a high mobility-to-size ratio. To accomplish high mobility the robot uses tumbling as its form of locomotion. By actively involving the body of the robot in the locomotion it can scale larger obstacles and will not get stuck in compliant terrain like similar sized wheeled robots. To accommodate real-world environments the new design has been waterproofed and moreover can be completely submerged in water to operate on a lake or stream floor. Additionally, this robot is equipped with a buoyancy control unit which will allow the robot to either sink or float in water, offering many unique applications in environmental monitoring and surveillance. This paper describes a first generation, radio controlled prototype of the design.