  Aerial-aquatic vehicles are capable to move in the two most dominant fluids,
making them more promising for a wide range of applications. We propose a
prototype with special designs for propulsion and thruster configuration to
cope with the vast differences in the fluid properties of water and air. For
propulsion, the operating range is switched for the different mediums by the
dual-speed propulsion unit, providing sufficient thrust and also ensuring
output efficiency. For thruster configuration, thrust vectoring is realized by
the rotation of the propulsion unit around the mount arm, thus enhancing the
underwater maneuverability. This paper presents a quadrotor prototype of this
concept and the design details and realization in practice.
